Sql plsql

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INTRODUCTION

SQL is divided into the following

 Data Definition Language (DDL)

 Data Manipulation Language (DML)
 Data Retrieval Language (DRL)
 Transaction Control Language (TCL)
 Data Control Language (DCL)

DDL -- create, alter, drop, truncate, rename
DML -- insert, update, delete
DRL -- select
TCL -- commit, rollback, savepoint
DCL -- grant, revoke

CREATE TABLE SYNTAX

Create table <table_name> (col1 datatype1, col2 datatype2 …coln datatypen);
Ex:
SQL> create table student (no number (2), name varchar (10), marks number (3));

INSERT

This will be used to insert the records into table.
We have two methods to insert.
 By value method
 By address method

a) USING VALUE METHOD

Syntax:
insert into <table_name) values (value1, value2, value3 …. Valuen);

© Copy rights are reserved.

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Ex:
SQL> insert into student values (1, ’sudha’, 100);
SQL> insert into student values (2, ’saketh’, 200);

To insert a new record again you have to type entire insert command, if there are lot of
records this will be difficult.
This will be avoided by using address method.

b) USING ADDRESS METHOD

Syntax:
insert into <table_name) values (&col1, &col2, &col3 …. &coln);
This will prompt you for the values but for every insert you have to use forward slash.

Ex:
SQL> insert into student values (&no, '&name', &marks);

Enter value for no: 1
Enter value for name: Jagan
Enter value for marks: 300
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(1, 'Jagan', 300)

SQL> /
Enter value for name: Naren
Enter value for marks: 400
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(2, 'Naren', 400)

c) INSERTING DATA INTO SPECIFIED COLUMNS USING VALUE METHOD

Syntax:
insert into <table_name)(col1, col2, col3 … Coln) values (value1, value2, value3
….


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Valuen);
Ex:
SQL> insert into student (no, name) values (3, ’Ramesh’);
SQL> insert into student (no, name) values (4, ’Madhu’);

d) INSERTING DATA INTO SPECIFIED COLUMNS USING ADDRESS METHOD

Syntax:
insert into <table_name)(col1, col2, col3 … coln) values (&col1, &col2 ….&coln);
This will prompt you for the values but for every insert you have to use forward slash.

Ex:
SQL> insert into student (no, name) values (&no, '&name');
Enter value for name: Visu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(5, 'Visu')

SQL> /
Enter value for name: Rattu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(6, 'Rattu')

SELECTING DATA

Syntax:
Select * from <table_name>; -- here * indicates all columns
or
Select col1, col2, … coln from <table_name>;

Ex:
SQL> select * from student;

NO NAME MARKS


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--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select no, name, marks from student;

NO NAME MARKS
--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select no, name from student;

NO NAME
--- -------
1 Sudha
2 Saketh
1 Jagan
2 Naren
3 Ramesh
4 Madhu
5 Visu
6 Rattu


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CONDITIONAL SELECTIONS AND OPERATORS

We have two clauses used in this
 Where
 Order by

USING WHERE

Syntax:
select * from <table_name> where <condition>;

the following are the different types of operators used in where clause.

 Arithmetic operators

 Comparison operators
 Logical operators

 Arithmetic operators -- highest precedence
+, -, *, /

 Comparison operators
 =, !=, >, <, >=, <=, <>

 between, not between
 in, not in
 null, not null
 like

 Logical operators

 And

 Or -- lowest precedence

 not

a) USING =, >, <, >=, <=, !=, <>


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Ex:
SQL> select * from student where no = 2;

NO NAME MARKS
--- ------- ---------
2 Saketh 200
2 Naren 400

SQL> select * from student where no < 2;

NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300

SQL> select * from student where no > 2;

NO NAME MARKS
--- ------- ----------
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select * from student where no <= 2;

NO NAME MARKS
--- ------- ----------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400

SQL> select * from student where no >= 2;


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NO NAME MARKS
--- ------- ---------
2 Saketh 200
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select * from student where no != 2;

NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select * from student where no <> 2;

NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300
3 Ramesh
4 Madhu
5 Visu
6 Rattu

b) USING AND

This will gives the output when all the conditions become true.


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Syntax:
select * from <table_name> where <condition1> and <condition2> and ..
<conditionn>;
Ex:
SQL> select * from student where no = 2 and marks >= 200;

NO NAME MARKS
--- ------- --------
2 Saketh 200
2 Naren 400

c) USING OR

This will gives the output when either of the conditions become true.

Syntax:
select * from <table_name> where <condition1> and <condition2> or ..
<conditionn>;
Ex:
SQL> select * from student where no = 2 or marks >= 200;

NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400

d) USING BETWEEN

This will gives the output based on the column and its lower bound, upperbound.

Syntax:
select * from <table_name> where <col> between <lower bound> and <upper
bound>;


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Ex:
SQL> select * from student where marks between 200 and 400;

NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400

e) USING NOT BETWEEN

This will gives the output based on the column which values are not in its lower bound,
upperbound.

Syntax:
select * from <table_name> where <col> not between <lower bound> and <upper
bound>;
Ex:
SQL> select * from student where marks not between 200 and 400;

NO NAME MARKS
--- ------- ---------
1 Sudha 100

f) USING IN

This will gives the output based on the column and its list of values specified.

Syntax:
select * from <table_name> where <col> in ( value1, value2, value3 … valuen);

Ex:
SQL> select * from student where no in (1, 2, 3);

NO NAME MARKS


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--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh

g) USING NOT IN

This will gives the output based on the column which values are not in the list of
values specified.

Syntax:
select * from <table_name> where <col> not in ( value1, value2, value3 … valuen);

Ex:
SQL> select * from student where no not in (1, 2, 3);

NO NAME MARKS
--- ------- ---------
4 Madhu
5 Visu
6 Rattu

h) USING NULL

This will gives the output based on the null values in the specified column.

Syntax:
select * from <table_name> where <col> is null;

Ex:
SQL> select * from student where marks is null;

NO NAME MARKS


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--- ------- ---------
3 Ramesh
4 Madhu
5 Visu
6 Rattu

i) USING NOT NULL

This will gives the output based on the not null values in the specified column.

Syntax:
select * from <table_name> where <col> is not null;

Ex:
SQL> select * from student where marks is not null;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400

j) USING LIKE

This will be used to search through the rows of database column based on the pattern
you specify.

Syntax:
select * from <table_name> where <col> like <pattern>;

Ex:
i) This will give the rows whose marks are 100.

SQL> select * from student where marks like 100;


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NO NAME MARKS
--- ------- ---------
1 Sudha 100
ii) This will give the rows whose name start with ‘S’.

SQL> select * from student where name like 'S%';

NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200

iii) This will give the rows whose name ends with ‘h’.

SQL> select * from student where name like '%h';

NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh

iV) This will give the rows whose name’s second letter start with ‘a’.

SQL> select * from student where name like '_a%';

NO NAME MARKS
--- ------- --------
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
6 Rattu

V) This will give the rows whose name’s third letter start with ‘d’.


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SQL> select * from student where name like '__d%';

NO NAME MARKS
--- ------- ---------
1 Sudha 100
4 Madhu

Vi) This will give the rows whose name’s second letter start with ‘t’ from ending.

SQL> select * from student where name like '%_t%';

NO NAME MARKS
--- ------- ---------
2 Saketh 200
6 Rattu

Vii) This will give the rows whose name’s third letter start with ‘e’ from ending.

SQL> select * from student where name like '%e__%';

NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh

Viii) This will give the rows whose name cotains 2 a’s.

SQL> select * from student where name like '%a% a %';

NO NAME MARKS
--- ------- ----------
1 Jagan 300

* You have to specify the patterns in like using underscore ( _ ).


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USING ORDER BY

This will be used to ordering the columns data (ascending or descending).

Syntax:
Select * from <table_name> order by <col> desc;
By default oracle will use ascending order.
If you want output in descending order you have to use desc keyword after the column.

Ex:
SQL> select * from student order by no;

NO NAME MARKS
--- ------- ---------
1 Sudha 100
1 Jagan 300
2 Saketh 200
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu

SQL> select * from student order by no desc;

NO NAME MARKS
--- ------- ---------
6 Rattu
5 Visu
4 Madhu
3 Ramesh
2 Saketh 200


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2 Naren 400
1 Sudha 100
1 Jagan 300

USING DML

USING UPDATE

This can be used to modify the table data.

Syntax:
Update <table_name> set <col1> = value1, <col2> = value2 where <condition>;

Ex:
SQL> update student set marks = 500;
If you are not specifying any condition this will update entire table.

SQL> update student set marks = 500 where no = 2;
SQL> update student set marks = 500, name = 'Venu' where no = 1;

USING DELETE

This can be used to delete the table data temporarily.

Syntax:
Delete <table_name> where <condition>;

Ex:
SQL> delete student;
If you are not specifying any condition this will delete entire table.

SQL> delete student where no = 2;


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USING DDL

USING ALTER

This can be used to add or remove columns and to modify the precision of the datatype.

a) ADDING COLUMN

Syntax:
alter table <table_name> add <col datatype>;

Ex:
SQL> alter table student add sdob date;

b) REMOVING COLUMN

Syntax:
alter table <table_name> drop <col datatype>;

Ex:
SQL> alter table student drop column sdob;

c) INCREASING OR DECREASING PRECISION OF A COLUMN

Syntax:
alter table <table_name> modify <col datatype>;
Ex:
SQL> alter table student modify marks number(5);

* To decrease precision the column should be empty.

d) MAKING COLUMN UNUSED


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Syntax:
alter table <table_name> set unused column <col>;
Ex:
SQL> alter table student set unused column marks;

Even though the column is unused still it will occupy memory.

d) DROPPING UNUSED COLUMNS

Syntax:
alter table <table_name> drop unused columns;

Ex:
SQL> alter table student drop unused columns;
* You can not drop individual unused columns of a table.

e) RENAMING COLUMN

Syntax:
alter table <table_name> rename column <old_col_name> to <new_col_name>;

Ex:
SQL> alter table student rename column marks to smarks;

USING TRUNCATE

This can be used to delete the entire table data permanently.
Syntax:
truncate table <table_name>;

Ex:
SQL> truncate table student;

USING DROP


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This will be used to drop the database object;

Syntax:
Drop table <table_name>;

Ex:
SQL> drop table student;

USING RENAME

This will be used to rename the database object;

Syntax:
rename <old_table_name> to <new_table_name>;

Ex:
SQL> rename student to stud;


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USING TCL

USING COMMIT

This will be used to save the work.
Commit is of two types.
 Implicit
 Explicit

a) IMPLICIT

This will be issued by oracle internally in two situations.
 When any DDL operation is performed.
 When you are exiting from SQL * PLUS.

b) EXPLICIT

This will be issued by the user.

Syntax:
Commit or commit work;
* When ever you committed then the transaction was completed.

USING ROLLBACK

This will undo the operation.
This will be applied in two methods.
 Upto previous commit
 Upto previous rollback

Syntax:
Roll or roll work;


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Or
Rollback or rollback work;
* While process is going on, if suddenly power goes then oracle will rollback the
transaction.
USING SAVEPOINT

You can use savepoints to rollback portions of your current set of transactions.

Syntax:
Savepoint <savepoint_name>;

Ex:
SQL> savepoint s1;
SQL> insert into student values(1, ‘a’, 100);
SQL> savepoint s2;
SQL> insert into student values(2, ‘b’, 200);
SQL> savepoint s3;
SQL> insert into student values(3, ‘c’, 300);
SQL> savepoint s4;
SQL> insert into student values(4, ‘d’, 400);

Before rollback


NO NAME MARKS
--- ------- ----------
1 a 100
2 b 200
3 c 300
4 d 400

SQL> rollback to savepoint s3;
Or
SQL> rollback to s3;


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This will rollback last two records.

NO NAME MARKS
--- ------- ----------
1 a 100
2 b 200


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USING DCL

DCL commands are used to granting and revoking the permissions.

USING GRANT

This is used to grant the privileges to other users.

Syntax:
Grant <privileges> on <object_name> to <user_name> [with grant option];

Ex:
SQL> grant select on student to sudha; -- you can give individual privilege
SQL> grant select, insert on student to sudha; -- you can give set of privileges
SQL> grant all on student to sudha; -- you can give all privileges

The sudha user has to use dot method to access the object.
SQL> select * from saketh.student;
The sudha user can not grant permission on student table to other users. To get this
type of option use the following.
SQL> grant all on student to sudha with grant option;
Now sudha user also grant permissions on student table.

USING REVOKE

This is used to revoke the privileges from the users to which you granted the privileges.

Syntax:
Revoke <privileges> on <object_name> from <user_name>;

Ex:
SQL> revoke select on student form sudha; -- you can revoke individual privilege
SQL> revoke select, insert on student from sudha; -- you can revoke set of privileges
SQL> revoke all on student from sudha; -- you can revoke all privileges


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USING ALIASES

CREATE WITH SELECT

We can create a table using existing table [along with data].

Syntax:
Create table <new_table_name> [col1, col2, col3 ... coln] as select * from
<old_table_name>;
Ex:
SQL> create table student1 as select * from student;

Creating table with your own column names.
SQL> create table student2(sno, sname, smarks) as select * from student;

Creating table with specified columns.
SQL> create table student3 as select no,name from student;

Creating table with out table data.
SQL> create table student2(sno, sname, smarks) as select * from student where 1 = 2;
In the above where clause give any condition which does not satisfy.

INSERT WITH SELECT

Using this we can insert existing table data to a another table in a single trip. But the
table structure should be same.

Syntax:
Insert into <table1> select * from <table2>;

Ex:
SQL> insert into student1 select * from student;

Inserting data into specified columns
SQL> insert into student1(no, name) select no, name from student;


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COLUMN ALIASES

Syntax:
Select <orginal_col> <alias_name> from <table_name>;

Ex:
SQL> select no sno from student;
or
SQL> select no “sno” from student;

TABLE ALIASES

If you are using table aliases you can use dot method to the columns.

Syntax:
Select <alias_name>.<col1>, <alias_name>.<col2> … <alias_name>.<coln> from
<table_name> <alias_name>;
Ex:
SQL> select s.no, s.name from student s;


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USING MERGE

MERGE

You can use merge command to perform insert and update in a single command.

Ex:

SQL> Merge into student1 s1
Using (select *From student2) s2
On(s1.no=s2.no)
When matched then
Update set marks = s2.marks
When not matched then
Insert (s1.no,s1.name,s1.marks)
Values(s2.no,s2.name,s2.marks);

In the above the two tables are with the same structure but we can merge different
structured tables also but the datatype of the columns should match.

Assume that student1 has columns like no,name,marks and student2 has columns like no,
name, hno, city.

SQL> Merge into student1 s1
Using (select *From student2) s2
On(s1.no=s2.no)
When matched then
Update set marks = s2.hno
When not matched then
Insert (s1.no,s1.name,s1.marks)
Values(s2.no,s2.name,s2.hno);


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MULTIBLE INSERTS

We have table called DEPT with the following columns and data

DEPTNO DNAME LOC
-------- -------- ----
10 accounting new york
20 research dallas
30 sales Chicago
40 operations boston

a) CREATE STUDENT TABLE

SQL> Create table student(no number(2),name varchar(2),marks number(3));

b) MULTI INSERT WITH ALL FIELDS

SQL> Insert all
Into student values(1,’a’,100)
Into student values(2,’b’,200)
Into student values(3,’c’,300)
Select *from dept where deptno=10;

-- This inserts 3 rows

c) MULTI INSERT WITH SPECIFIED FIELDS

SQL> insert all
Into student (no,name) values(4,’d’)
Into student(name,marks) values(’e’,400)



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d) MULTI INSERT WITH DUPLICATE ROWS

SQL> insert all
Into student values(1,’a’,100)
Into student values(2,’b’,200)
Select *from dept where deptno > 10;

-- This inserts 9 rows because in the select statement retrieves 3 records (3 inserts for
each row retrieved)

e) MULTI INSERT WITH CONDITIONS BASED

SQL> Insert all
When deptno > 10 then
Into student1 values(1,’a’,100)
When dname = ‘SALES’ then
Into student2 values(2,’b’,200)
When loc = ‘NEW YORK’ then
Into student3 values(3,’c’,300)
Select *from dept where deptno>10;

-- This inserts 4 rows because the first condition satisfied 3 times, second condition
satisfied once and the last none.

f) MULTI INSERT WITH CONDITIONS BASED AND ELSE

SQL> Insert all
When deptno > 100 then
When dname = ‘S’ then
Else


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Into student values(4,’d’,400)
Select *from dept where deptno>10;

-- This inserts 3 records because the else satisfied 3 times

g) MULTI INSERT WITH CONDITIONS BASED AND FIRST

SQL> Insert first
When deptno = 20 then
When dname = ‘RESEARCH’ then

-- This inserts 1 record because the first clause avoid to check the remaining
conditions once the condition is satisfied.

h) MULTI INSERT WITH CONDITIONS BASED, FIRST AND ELSE

SQL> Insert first
When deptno = 30 then
When dname = ‘R’ then
Else
Into student values(4,’d’,400)

-- This inserts 1 record because the else clause satisfied once


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i) MULTI INSERT WITH MULTIBLE TABLES

SQL> Insert all


** You can use multi tables with specified fields, with duplicate rows, with conditions,
with first and else clauses.


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FUNCTIONS

Functions can be categorized as follows.

 Single row functions
 Group functions

SINGLE ROW FUNCTIONS

Single row functions can be categorized into five. These will be applied for each row and
produces individual output for each row.

 Numeric functions
 String functions
 Date functions
 Miscellaneous functions
 Conversion functions

NUMERIC FUNCTIONS

 Abs
 Sign
 Sqrt
 Mod
 Nvl
 Power
 Exp
 Ln
 Log
 Ceil
 Floor
 Round
 Trunk
 Bitand
 Greatest


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 Least
 Coalesce
a) ABS

Absolute value is the measure of the magnitude of value.
Absolute value is always a positive number.

Syntax: abs (value)

Ex:
SQL> select abs(5), abs(-5), abs(0), abs(null) from dual;

ABS(5) ABS(-5) ABS(0) ABS(NULL)
---------- ---------- ---------- -------------
5 -5 0

b) SIGN

Sign gives the sign of a value.

Syntax: sign (value)

Ex:
SQL> select sign(5), sign(-5), sign(0), sign(null) from dual;

SIGN(5) SIGN(-5) SIGN(0) SIGN(NULL)
---------- ---------- ---------- --------------
1 -1 0

c) SQRT

This will give the square root of the given value.

Syntax: sqrt (value) -- here value must be positive.


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Ex:
SQL> select sqrt(4), sqrt(0), sqrt(null), sqrt(1) from dual;
SQRT(4) SQRT(0) SQRT(NULL) SQRT(1)
---------- ---------- --------------- ----------
2 0 1

d) MOD

This will give the remainder.

Syntax: mod (value, divisor)

Ex:
SQL> select mod(7,4), mod(1,5), mod(null,null), mod(0,0), mod(-7,4) from dual;

MOD(7,4) MOD(1,5) MOD(NULL,NULL) MOD(0,0) MOD(-7,4)
------------ ---------- --------------------- ----------- -------------
3 1 0 -3

e) NVL

This will substitutes the specified value in the place of null values.

Syntax: nvl (null_col, replacement_value)

Ex:
SQL> select * from student; -- here for 3rd row marks value is null

NO NAME MARKS
--- ------- ---------
1 a 100
2 b 200
3 c

SQL> select no, name, nvl(marks,300) from student;


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NO NAME NVL(MARKS,300)
--- ------- ---------------------
1 a 100
2 b 200
3 c 300

SQL> select nvl(1,2), nvl(2,3), nvl(4,3), nvl(5,4) from dual;

NVL(1,2) NVL(2,3) NVL(4,3) NVL(5,4)
---------- ---------- ---------- ----------
1 2 4 5

SQL> select nvl(0,0), nvl(1,1), nvl(null,null), nvl(4,4) from dual;

NVL(0,0) NVL(1,1) NVL(null,null) NVL(4,4)
---------- ---------- ----------------- ----------
0 1 4

f) POWER

Power is the ability to raise a value to a given exponent.

Syntax: power (value, exponent)

Ex:
SQL> select power(2,5), power(0,0), power(1,1), power(null,null), power(2,-5)
from dual;

POWER(2,5) POWER(0,0) POWER(1,1) POWER(NULL,NULL) POWER(2,-5)
-------------- -------------- ----- --------- ----------------------- ---------------
32 1 1 .03125

g) EXP

This will raise e value to the give power.


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Syntax: exp (value)
Ex:
SQL> select exp(1), exp(2), exp(0), exp(null), exp(-2) from dual;

EXP(1) EXP(2) EXP(0) EXP(NULL) EXP(-2)
-------- --------- -------- ------------- ----------
2.71828183 7.3890561 1 .135335283

h) LN

This is based on natural or base e logarithm.

Syntax: ln (value) -- here value must be greater than zero which is positive only.

Ex:
SQL> select ln(1), ln(2), ln(null) from dual;

LN(1) LN(2) LN(NULL)
------- ------- ------------
0 .693147181

Ln and Exp are reciprocal to each other.
EXP (3) = 20.0855369
LN (20.0855369) = 3

i) LOG

This is based on 10 based logarithm.

Syntax: log (10, value) -- here value must be greater than zero which is positive only.

Ex:
SQL> select log(10,100), log(10,2), log(10,1), log(10,null) from dual;


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LOG(10,100) LOG(10,2) LOG(10,1) LOG(10,NULL)
--------------- ----------- ------------ -----------------
2 .301029996 0

LN (value) = LOG (EXP(1), value)

SQL> select ln(3), log(exp(1),3) from dual;

LN(3) LOG(EXP(1),3)
------- -----------------
1.09861229 1.09861229

j) CEIL

This will produce a whole number that is greater than or equal to the specified value.

Syntax: ceil (value)

Ex:
SQL> select ceil(5), ceil(5.1), ceil(-5), ceil( -5.1), ceil(0), ceil(null) from dual;

CEIL(5) CEIL(5.1) CEIL(-5) CEIL(-5.1) CEIL(0) CEIL(NULL)
--------- ----------- ---------- ------------ -------- --------------
5 6 -5 -5 0
k) FLOOR

This will produce a whole number that is less than or equal to the specified value.

Syntax: floor (value)

Ex:
SQL> select floor(5), floor(5.1), floor(-5), floor( -5.1), floor(0), floor(null) from
dual;

FLOOR(5) FLOOR(5.1) FLOOR(-5) FLOOR(-5.1) FLOOR(0) FLOOR(NULL)


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----------- ------------- ------------ -------------- ----------- ----------------
5 5 -5 -6 0
l) ROUND

This will rounds numbers to a given number of digits of precision.

Syntax: round (value, precision)

Ex:
SQL> select round(123.2345), round(123.2345,2), round(123.2354,2) from dual;

ROUND(123.2345) ROUND(123.2345,0) ROUND(123.2345,2) ROUND(123.2354,2)
--------------------- ------------------------ ----------------------- -----------------------
123 123 123.23 123.24

SQL> select round(123.2345,-1), round(123.2345,-2), round(123.2345,-3),
round(123.2345,-4) from dual;

ROUND(123.2345,-1) ROUND(123.2345,-2) ROUND(123.2345,-3) ROUND(123.2345,-4)
------------------------ ------------------------- ------------------------ ------------------------
120 100 0 0

SQL> select round(123,0), round(123,1), round(123,2) from dual;

ROUND(123,0) ROUND(123,1) ROUND(123,2)
----------------- ----------------- ----------------
123 123 123

SQL> select round(-123,0), round(-123,1), round(-123,2) from dual;

ROUND(-123,0) ROUND(-123,1) ROUND(-123,2)
------------------ ----------------- -------------------
-123 -123 -123

SQL> select round(123,-1), round(123,-2), round(123,-3), round(-123,-1), round(
-123,-2), round(-123,-3) from dual;


37

ROUND(123,-1) ROUND(123,-2) ROUND(123,-3) ROUND(-123,-1) ROUND(-123,-2)
ROUND(-123,-3)
------------- ------------- ------------- -------------- -------------- --------------------------
120 100 0 -120 -100 0

SQL> select round(null,null), round(0,0), round(1,1), round(-1,-1), round(-2,-2)
from dual;

ROUND(NULL,NULL) ROUND(0,0) ROUND(1,1) ROUND(-1,-1) ROUND(-2,-2)
----------------------- -------------- -------------- ---------------- ----------------
0 1 0 0

m) TRUNC

This will truncates or chops off digits of precision from a number.

Syntax: trunc (value, precision)

Ex:
SQL> select trunc(123.2345), trunc(123.2345,2), trunc(123.2354,2) from dual;

TRUNC(123.2345) TRUNC(123.2345,2) TRUNC(123.2354,2)
--------------------- ----------------------- -----------------------
123 123.23 123.23

SQL> select trunc(123.2345,-1), trunc(123.2345,-2), trunc(123.2345,-3),
trunc(123.2345,-4) from dual;

TRUNC(123.2345,-1) TRUNC(123.2345,-2) TRUNC(123.2345,-3) TRUNC(123.2345,-4)
------------------------ ------------------------ ----------------------- ------------------------
120 100 0 0

SQL> select trunc(123,0), trunc(123,1), trunc(123,2) from dual;


38

TRUNC(123,0) TRUNC(123,1) TRUNC(123,2)
---------------- ---------------- -----------------
123 123 123

SQL> select trunc(-123,0), trunc(-123,1), trunc(-123,2) from dual;

TRUNC(-123,0) TRUNC(-123,1) TRUNC(-123,2)
----------------- ----------------- -----------------
-123 -123 -123

SQL> select trunc(123,-1), trunc(123,-2), trunc(123,-3), trunc(-123,-1), trunc(
-123,2), trunc(-123,-3) from dual;

TRUNC(123,-1) TRUNC(123,-2) TRUNC(123,-3) TRUNC(-123,-1) TRUNC(-123,2) TRUNC(-
123,-3)
------------- ------------- ------------- -------------- ------------- ---------------------------------
120 100 0 -120 -123 0

SQL> select trunc(null,null), trunc(0,0), trunc(1,1), trunc(-1,-1), trunc(-2,-2) from
dual;

TRUNC(NULL,NULL) TRUNC(0,0) TRUNC(1,1) TRUNC(-1,-1) TRUNC(-2,-2)
----------------------- ------------- ------------- --------------- ----------------
0 1 0 0

n) BITAND

This will perform bitwise and operation.

Syntax: bitand (value1, value2)

Ex:


39

SQL> select bitand(2,3), bitand(0,0), bitand(1,1), bitand(null,null), bitand(-2,-3)
from dual;
BITAND(2,3) BITAND(0,0) BITAND(1,1) BITAND(NULL,NULL) BITAND(-2,-3)
-------------- --------------- -------------- ------------------------ -----------------
2 0 1 -4

o) GREATEST

This will give the greatest number.

Syntax: greatest (value1, value2, value3 … valuen)

Ex:
SQL> select greatest(1, 2, 3), greatest(-1, -2, -3) from dual;

GREATEST(1,2,3) GREATEST(-1,-2,-3)
-------------------- -----------------------
3 -1

 If all the values are zeros then it will display zero.
 If all the parameters are nulls then it will display nothing.
 If any of the parameters is null it will display nothing.

p) LEAST

This will give the least number.

Syntax: least (value1, value2, value3 … valuen)

Ex:
SQL> select least(1, 2, 3), least(-1, -2, -3) from dual;

LEAST(1,2,3) LEAST(-1,-2,-3)
-------------------- -----------------------
1 -3
 If all the values are zeros then it will display zero.


40

q) COALESCE

This will return first non-null value.

Syntax: coalesce (value1, value2, value3 … valuen)

Ex:
SQL> select coalesce(1,2,3), coalesce(null,2,null,5) from dual;

COALESCE(1,2,3) COALESCE(NULL,2,NULL,5)
------------------- -------------------------------
1 2

STRING FUNCTIONS

 Initcap
 Upper
 Lower
 Length
 Rpad
 Lpad
 Ltrim
 Rtrim
 Trim
 Translate
 Replace
 Soundex
 Concat ( ‘ || ‘ Concatenation operator)
 Ascii
 Chr
 Substr
 Instr
 Decode
 Greatest


41

 Least
 Coalesce
a) INITCAP

This will capitalize the initial letter of the string.

Syntax: initcap (string)

Ex:
SQL> select initcap('computer') from dual;

INITCAP
-----------
Computer

b) UPPER

This will convert the string into uppercase.

Syntax: upper (string)

Ex:
SQL> select upper('computer') from dual;
UPPER
-----------
COMPUTER

c) LOWER

This will convert the string into lowercase.

Syntax: lower (string)

Ex:
SQL> select lower('COMPUTER') from dual;


42

LOWER
-----------
computer

d) LENGTH

This will give length of the string.

Syntax: length (string)

Ex:
SQL> select length('computer') from dual;

LENGTH
-----------
8

e) RPAD

This will allows you to pad the right side of a column with any set of characters.

Syntax: rpad (string, length [, padding_char])

Ex:
SQL> select rpad('computer',15,'*'), rpad('computer',15,'*#') from dual;

RPAD('COMPUTER' RPAD('COMPUTER'
---------------------- ----------------------
computer******* computer*#*#*#*

-- Default padding character was blank space.

f) LPAD


43

This will allows you to pad the left side of a column with any set of characters.
Syntax: lpad (string, length [, padding_char])

Ex:
SQL> select lpad('computer',15,'*'), lpad('computer',15,'*#') from dual;

LPAD('COMPUTER' LPAD('COMPUTER'
--------------------- ---------------------
*******computer *#*#*#*computer

-- Default padding character was blank space.

g) LTRIM

This will trim off unwanted characters from the left end of string.

Syntax: ltrim (string [,unwanted_chars])

Ex:
SQL> select ltrim('computer','co'), ltrim('computer','com') from dual;

LTRIM( LTRIM
-------- ---------
mputer puter

SQL> select ltrim('computer','puter'), ltrim('computer','omputer') from dual;

LTRIM('C LTRIM('C
---------- ----------
computer computer

-- If you haven’t specify any unwanted characters it will display entire string.

h) RTRIM


44

This will trim off unwanted characters from the right end of string.
Syntax: rtrim (string [, unwanted_chars])

Ex:
SQL> select rtrim('computer','er'), rtrim('computer','ter') from dual;
RTRIM( RTRIM
-------- ---------
comput compu

SQL> select rtrim('computer','comput’), rtrim('computer','compute') from dual;

RTRIM('C RTRIM('C
---------- ----------
computer computer
-- If you haven’t specify any unwanted characters it will display entire string.

i) TRIM

This will trim off unwanted characters from the both sides of string.

Syntax: trim (unwanted_chars from string)

Ex:
SQL> select trim( 'i' from 'indiani') from dual;

TRIM(
-----
ndian

SQL> select trim( leading'i' from 'indiani') from dual; -- this will work as LTRIM

TRIM(L
------
ndiani


45

SQL> select trim( trailing'i' from 'indiani') from dual; -- this will work as RTRIM

TRIM(T
------
Indian

j) TRANSLATE

This will replace the set of characters, character by character.

Syntax: translate (string, old_chars, new_chars)

Ex:
SQL> select translate('india','in','xy') from dual;

TRANS
--------
xydxa

k) REPLACE

This will replace the set of characters, string by string.

Syntax: replace (string, old_chars [, new_chars])

Ex:
SQL> select replace('india','in','xy'), replace(‘india’,’in’) from dual;

REPLACE REPLACE
----------- -----------
Xydia dia

l) SOUNDEX


46

This will be used to find words that sound like other words, exclusively used in where
clause.
Syntax: soundex (string)

Ex:
SQL> select * from emp where soundex(ename) = soundex('SMIT');

EMPNO ENAME JOB MGR HIREDATE SAL DEPTNO
-------- -------- ----- ----- ------------ --------- ----------
7369 SMITH CLERK 7902 17-DEC-80 500 20

m) CONCAT

This will be used to combine two strings only.

Syntax: concat (string1, string2)

Ex:
SQL> select concat('computer',' operator') from dual;

CONCAT('COMPUTER'
-------------------------
computer operator

If you want to combine more than two strings you have to use concatenation
operator(||).

SQL> select 'how' || ' are' || ' you' from dual;

'HOW'||'ARE
---------------
how are you

n) ASCII


47

This will return the decimal representation in the database character set of the first
character of the string.

Syntax: ascii (string)

Ex:
SQL> select ascii('a'), ascii('apple') from dual;

ASCII('A') ASCII('APPLE')
------------ ------------------
97 97

o) CHR

This will return the character having the binary equivalent to the string in either the
database character set or the national character set.

Syntax: chr (number)

Ex:
SQL> select chr(97) from dual;

CHR
-----
a

p) SUBSTR

This will be used to extract substrings.

Syntax: substr (string, start_chr_count [, no_of_chars])

Ex:
SQL> select substr('computer',2), substr('computer',2,5), substr('computer',3,7)
from dual;


48

SUBSTR( SUBST SUBSTR
---------- ------- --------
omputer omput mputer

 If no_of_chars parameter is negative then it will display nothing.
 If both parameters except string are null or zeros then it will display nothing.
 If no_of_chars parameter is greater than the length of the string then it
ignores and calculates based on the orginal string length.

 If start_chr_count is negative then it will extract the substring from right
end.

1 2 3 4 5 6 7 8

C O M P U T E R

-8 -7 -6 -5 -4 -3 -2 -1

q) INSTR

This will allows you for searching through a string for set of characters.

Syntax: instr (string, search_str [, start_chr_count [, occurrence] ])

Ex:
SQL> select instr('information','o',4,1), instr('information','o',4,2) from dual;

INSTR('INFORMATION','O',4,1) INSTR('INFORMATION','O',4,2)
------------------------------------ -------------------------------------
4 10

 If you are not specifying start_chr_count and occurrence then it will start
search from the beginning and finds first occurrence only.

 If both parameters start_chr_count and occurrence are null, it will display
nothing.


49

r) DECODE

Decode will act as value by value substitution.
For every value of field, it will checks for a match in a series of if/then tests.

Syntax: decode (value, if1, then1, if2, then2, ……. else);

Ex:
SQL> select sal, decode(sal,500,'Low',5000,'High','Medium') from emp;

SAL DECODE
----- ---------
500 Low
2500 Medium
2000 Medium
3500 Medium
3000 Medium
5000 High
4000 Medium
5000 High
1800 Medium
1200 Medium
2000 Medium
2700 Medium
2200 Medium
3200 Medium

SQL> select decode(1,1,3), decode(1,2,3,4,4,6) from dual;

DECODE(1,1,3) DECODE(1,2,3,4,4,6)
----------------- ------------------------
3 6

 If the number of parameters are odd and different then decode will display
nothing.
 If the number of parameters are even and different then decode will display last
value.


50

 If all the parameters are null then decode will display nothing.
 If all the parameters are zeros then decode will display zero.

s) GREATEST

This will give the greatest string.

Syntax: greatest (strng1, string2, string3 … stringn)

Ex:
SQL> select greatest('a', 'b', 'c'), greatest('satish','srinu','saketh') from dual;

GREAT GREAT
------- -------
c srinu


t) LEAST

This will give the least string.

Syntax: greatest (strng1, string2, string3 … stringn)

Ex:
SQL> select least('a', 'b', 'c'), least('satish','srinu','saketh') from dual;

LEAST LEAST
------- -------
a saketh



51

u) COALESCE

This will gives the first non-null string.

Syntax: coalesce (strng1, string2, string3 … stringn)

Ex:
SQL> select coalesce('a','b','c'), coalesce(null,'a',null,'b') from dual;

COALESCE COALESCE
----------- -----------
a a

DATE FUNCTIONS

 Sysdate
 Current_date
 Current_timestamp
 Systimestamp
 Localtimestamp
 Dbtimezone
 Sessiontimezone
 To_char
 To_date
 Add_months
 Months_between
 Next_day
 Last_day
 Extract
 Greatest
 Least
 Round
 Trunc
 New_time
 Coalesce


52

Oracle default date format is DD-MON-YY.
We can change the default format to our desired format by using the following command.

SQL> alter session set nls_date_format = ‘DD-MONTH-YYYY’;
But this will expire once the session was closed.

a) SYSDATE

This will give the current date and time.
Ex:
SQL> select sysdate from dual;

SYSDATE
-----------
24-DEC-06

b) CURRENT_DATE

This will returns the current date in the session’s timezone.

Ex:
SQL> select current_date from dual;

CURRENT_DATE
------------------
24-DEC-06

c) CURRENT_TIMESTAMP

This will returns the current timestamp with the active time zone information.

Ex:
SQL> select current_timestamp from dual;

CURRENT_TIMESTAMP
---------------------------------------------------------------------------


53

24-DEC-06 03.42.41.383369 AM +05:30

d) SYSTIMESTAMP

This will returns the system date, including fractional seconds and time zone of the
database.

Ex:
SQL> select systimestamp from dual;
SYSTIMESTAMP
---------------------------------------------------------------------------
24-DEC-06 03.49.31.830099 AM +05:30

e) LOCALTIMESTAMP

This will returns local timestamp in the active time zone information, with no time
zone information shown.

Ex:
SQL> select localtimestamp from dual;

LOCALTIMESTAMP
---------------------------------------------------------------------------
24-DEC-06 03.44.18.502874 AM

f) DBTIMEZONE

This will returns the current database time zone in UTC format. (Coordinated Universal
Time)

Ex:
SQL> select dbtimezone from dual;

DBTIMEZONE
---------------
-07:00

g) SESSIONTIMEZONE


54

This will returns the value of the current session’s time zone.

Ex:
SQL> select sessiontimezone from dual;

SESSIONTIMEZONE
------------------------------------
+05:30

h) TO_CHAR

This will be used to extract various date formats.
The available date formats as follows.

Syntax: to_char (date, format)

DATE FORMATS

D -- No of days in week
DD -- No of days in month
DDD -- No of days in year
MM -- No of month
MON -- Three letter abbreviation of month
MONTH -- Fully spelled out month
RM -- Roman numeral month
DY -- Three letter abbreviated day
DAY -- Fully spelled out day
Y -- Last one digit of the year
YY -- Last two digits of the year
YYY -- Last three digits of the year
YYYY -- Full four digit year
SYYYY -- Signed year
I -- One digit year from ISO standard
IY -- Two digit year from ISO standard


55

IYY -- Three digit year from ISO standard
IYYY -- Four digit year from ISO standard
Y, YYY -- Year with comma
YEAR -- Fully spelled out year
CC -- Century
Q -- No of quarters
W -- No of weeks in month
WW -- No of weeks in year
IW -- No of weeks in year from ISO standard
HH -- Hours
MI -- Minutes
SS -- Seconds
FF -- Fractional seconds
AM or PM -- Displays AM or PM depending upon time of day
A.M or P.M -- Displays A.M or P.M depending upon time of day
AD or BC -- Displays AD or BC depending upon the date
A.D or B.C -- Displays AD or BC depending upon the date
FM -- Prefix to month or day, suppresses padding of month or day
TH -- Suffix to a number
SP -- suffix to a number to be spelled out
SPTH -- Suffix combination of TH and SP to be both spelled out
THSP -- same as SPTH

Ex:
SQL> select to_char(sysdate,'dd month yyyy hh:mi:ss am dy') from dual;

TO_CHAR(SYSDATE,'DD MONTH YYYYHH:MI
----------------------------------------------------
24 december 2006 02:03:23 pm sun

SQL> select to_char(sysdate,'dd month year') from dual;

TO_CHAR(SYSDATE,'DDMONTHYEAR')
-------------------------------------------------------


56

24 december two thousand six

SQL> select to_char(sysdate,'dd fmmonth year') from dual;

TO_CHAR(SYSDATE,'DD FMMONTH YEAR')
-------------------------------------------------------
24 december two thousand six

SQL> select to_char(sysdate,'ddth DDTH') from dual;

TO_CHAR(S
------------
24th 24TH

SQL> select to_char(sysdate,'ddspth DDSPTH') from dual;

TO_CHAR(SYSDATE,'DDSPTHDDSPTH
------------------------------------------
twenty-fourth TWENTY-FOURTH

SQL> select to_char(sysdate,'ddsp Ddsp DDSP ') from dual;

TO_CHAR(SYSDATE,'DDSPDDSPDDSP')
------------------------------------------------
twenty-four Twenty-Four TWENTY-FOUR

i) TO_DATE

This will be used to convert the string into data format.

Syntax: to_date (date)

Ex:
SQL> select to_char(to_date('24/dec/2006','dd/mon/yyyy'), 'dd * month * day')
from dual;


57

TO_CHAR(TO_DATE('24/DEC/20
--------------------------
24 * december * Sunday

-- If you are not using to_char oracle will display output in default date format.

j) ADD_MONTHS

This will add the specified months to the given date.

Syntax: add_months (date, no_of_months)

Ex:
SQL> select add_months(to_date('11-jan-1990','dd-mon-yyyy'), 5) from dual;

ADD_MONTHS
----------------
11-JUN-90

SQL> select add_months(to_date('11-jan-1990','dd-mon-yyyy'), -5) from dual;

ADD_MONTH
---------------
11-AUG-89

 If no_of_months is zero then it will display the same date.
 If no_of_months is null then it will display nothing.

k) MONTHS_BETWEEN

This will give difference of months between two dates.

Syntax: months_between (date1, date2)

Ex:


58

SQL> select months_between(to_date('11-aug-1990','dd-mon-yyyy'), to_date('11-
jan-1990','dd-mon-yyyy')) from dual;

MONTHS_BETWEEN(TO_DATE('11-AUG-1990','DD-MON-YYYY'),TO_DATE('11-JAN-
1990','DD-MON-YYYY'))
-----------------------------------------------------------------------------------------------
7
SQL> select months_between(to_date('11-jan-1990','dd-mon-yyyy'), to_date('11-
aug-1990','dd-mon-yyyy')) from dual;

MONTHS_BETWEEN(TO_DATE('11-JAN-1990','DD-MON-YYYY'),TO_DATE('11-AUG-
1990','DD-MON-YYYY'))
-------------------------------------------------------------------------------------------------
-7

l) NEXT_DAY

This will produce next day of the given day from the specified date.

Syntax: next_day (date, day)

Ex:
SQL> select next_day(to_date('24-dec-2006','dd-mon-yyyy'),'sun') from dual;

NEXT_DAY(
-------------
31-DEC-06

-- If the day parameter is null then it will display nothing.

m) LAST_DAY

This will produce last day of the given date.


59

Syntax: last_day (date)

Ex:
SQL> select last_day(to_date('24-dec-2006','dd-mon-yyyy'),'sun') from dual;
LAST_DAY(
-------------
31-DEC-06

n) EXTRACT

This is used to extract a portion of the date value.

Syntax: extract ((year | month | day | hour | minute | second), date)

Ex:
SQL> select extract(year from sysdate) from dual;
EXTRACT(YEARFROMSYSDATE)
------------------------------------
2006

-- You can extract only one value at a time.

o) GREATEST

This will give the greatest date.

Syntax: greatest (date1, date2, date3 … daten)

Ex:
SQL> select greatest(to_date('11-jan-90','dd-mon-yy'),to_date('11-mar-90','dd-
mon-yy'),to_date('11-apr-90','dd-mon-yy')) from dual;

GREATEST(
-------------


60

11-APR-90

p) LEAST

This will give the least date.
Syntax: least (date1, date2, date3 … daten)

Ex:
SQL> select least(to_date('11-jan-90','dd-mon-yy'),to_date('11-mar-90','dd-mon-
yy'),to_date('11-apr-90','dd-mon-yy')) from dual;

LEAST(
-------------
11-JAN-90

q) ROUND

Round will rounds the date to which it was equal to or greater than the given date.

Syntax: round (date, (day | month | year))

If the second parameter was year then round will checks the month of the given date in
the following ranges.

JAN -- JUN
JUL -- DEC

If the month falls between JAN and JUN then it returns the first day of the current year.
If the month falls between JUL and DEC then it returns the first day of the next year.

If the second parameter was month then round will checks the day of the given date in
the following ranges.

1 -- 15
16 -- 31


61

If the day falls between 1 and 15 then it returns the first day of the current month.
If the day falls between 16 and 31 then it returns the first day of the next month.

If the second parameter was day then round will checks the week day of the given date
in the following ranges.

SUN -- WED
THU -- SUN

If the week day falls between SUN and WED then it returns the previous sunday.
If the weekday falls between THU and SUN then it returns the next sunday.

 If the second parameter was null then it returns nothing.

 If the you are not specifying the second parameter then round will resets the time
to the begining of the current day in case of user specified date.

 If the you are not specifying the second parameter then round will resets the time
to the begining of the next day in case of sysdate.

Ex:
SQL> select round(to_date('24-dec-04','dd-mon-yy'),'year'), round(to_date('11-mar-
06','dd-mon-yy'),'year') from dual;

ROUND(TO_ ROUND(TO_
------------ ---------------
01-JAN-05 01-JAN-06

SQL> select round(to_date('11-jan-04','dd-mon-yy'),'month'), round(to_date('18-
jan-04','dd-mon-yy'),'month') from dual;

ROUND(TO_ ROUND(TO_
------------- ---------------
01-JAN-04 01-FEB-04

SQL> select round(to_date('26-dec-06','dd-mon-yy'),'day'), round(to_date('29-dec-
06','dd-mon-yy'),'day') from dual;


62

ROUND(TO_ ROUND(TO_
-------------- --------------
24-DEC-06 31-DEC-06

SQL> select to_char(round(to_date('24-dec-06','dd-mon-yy')), 'dd mon yyyy
hh:mi:ss am') from dual;
TO_CHAR(ROUND(TO_DATE('
---------------------------------
24 dec 2006 12:00:00 am
r) TRUNC

Trunc will chops off the date to which it was equal to or less than the given date.

Syntax: trunc (date, (day | month | year))

 If the second parameter was year then it always returns the first day of the current
year.

 If the second parameter was month then it always returns the first day of the
current month.

 If the second parameter was day then it always returns the previous sunday.
 If the second parameter was null then it returns nothing.
 If the you are not specifying the second parameter then trunk will resets the time
to the begining of the current day.

Ex:
SQL> select trunc(to_date('24-dec-04','dd-mon-yy'),'year'), trunc(to_date('11-mar-
06','dd-mon-yy'),'year') from dual;

TRUNC(TO_ TRUNC(TO_
------------- --------------
01-JAN-04 01-JAN-06

SQL> select trunc(to_date('11-jan-04','dd-mon-yy'),'month'), trunc(to_date('18-jan-
04','dd-mon-yy'),'month') from dual;


63

TRUNC(TO_ TRUNC(TO_
------------- -------------
01-JAN-04 01-JAN-04

SQL> select trunc(to_date('26-dec-06','dd-mon-yy'),'day'), trunc(to_date('29-dec-
06','dd-mon-yy'),'day') from dual;
TRUNC(TO_ TRUNC(TO_
------------- --------------
24-DEC-06 24-DEC-06

SQL> select to_char(trunc(to_date('24-dec-06','dd-mon-yy')), 'dd mon yyyy hh:mi:ss
am') from dual;

TO_CHAR(TRUNC(TO_DATE('
---------------------------------
24 dec 2006 12:00:00 am

s) NEW_TIME

This will give the desired timezone’s date and time.

Syntax: new_time (date, current_timezone, desired_timezone)

Available timezones are as follows.

TIMEZONES

AST/ADT -- Atlantic standard/day light time
BST/BDT -- Bering standard/day light time
CST/CDT -- Central standard/day light time
EST/EDT -- Eastern standard/day light time
GMT -- Greenwich mean time
HST/HDT -- Alaska-Hawaii standard/day light time
MST/MDT -- Mountain standard/day light time
NST -- Newfoundland standard time
PST/PDT -- Pacific standard/day light time


64

YST/YDT -- Yukon standard/day light time

Ex:
SQL> select to_char(new_time(sysdate,'gmt','yst'),'dd mon yyyy hh:mi:ss am') from
dual;

TO_CHAR(NEW_TIME(SYSDAT
-----------------------------------
24 dec 2006 02:51:20 pm

SQL> select to_char(new_time(sysdate,'gmt','est'),'dd mon yyyy hh:mi:ss am') from
dual;

TO_CHAR(NEW_TIME(SYSDAT
-----------------------
24 dec 2006 06:51:26 pm

t) COALESCE

This will give the first non-null date.

Syntax: coalesce (date1, date2, date3 … daten)

Ex:
SQL> select coalesce('12-jan-90','13-jan-99'), coalesce(null,'12-jan-90','23-mar-
98',null) from dual;

COALESCE( COALESCE(
------------- ------------
12-jan-90 12-jan-90

MISCELLANEOUS FUNCTIONS

 Uid
 User
 Vsize


65

 Rank
 Dense_rank

a) UID

This will returns the integer value corresponding to the user currently logged in.

Ex:
SQL> select uid from dual;

UID
----------
319

b) USER

This will returns the login’s user name.

Ex:
SQL> select user from dual;

USER
----------------
SAKETH

c) VSIZE

This will returns the number of bytes in the expression.

Ex:
SQL> select vsize(123), vsize('computer'), vsize('12-jan-90') from dual;

VSIZE(123) VSIZE('COMPUTER') VSIZE('12-JAN-90')
------------- ----------------------- ----------------------
3 8 9


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d) RANK

This will give the non-sequential ranking.

Ex:
SQL> select rownum,sal from (select sal from emp order by sal desc);
ROWNUM SAL
---------- ----------
1 5000
2 3000
3 3000
4 2975
5 2850
6 2450
7 1600
8 1500
9 1300
10 1250
11 1250
12 1100
13 1000
14 950
15 800

SQL> select rank(2975) within group(order by sal desc) from emp;

RANK(2975)WITHINGROUP(ORDERBYSALDESC)
---------------------------------------------------------
4

d) DENSE_RANK

This will give the sequential ranking.

Ex:


67

SQL> select dense_rank(2975) within group(order by sal desc) from emp;

DENSE_RANK(2975)WITHINGROUP(ORDERBYSALDESC)
-----------------------------------------------------------------
3

CONVERSION FUNCTIONS

 Bin_to_num
 Chartorowid
 Rowidtochar
 To_number
 To_char
 To_date
a) BIN_TO_NUM

This will convert the binary value to its numerical equivalent.

Syntax: bin_to_num( binary_bits)

Ex:
SQL> select bin_to_num(1,1,0) from dual;

BIN_TO_NUM(1,1,0)
------------------------
6

 If all the bits are zero then it produces zero.
 If all the bits are null then it produces an error.

b) CHARTOROWID

This will convert a character string to act like an internal oracle row identifier or rowid.

c) ROWIDTOCHAR


68

This will convert an internal oracle row identifier or rowid to character string.

d) TO_NUMBER

This will convert a char or varchar to number.

e) TO_CHAR

This will convert a number or date to character string.

f) TO_DATE

This will convert a number, char or varchar to a date.

GROUP FUNCTIONS

 Sum
 Avg
 Max
 Min
 Count

Group functions will be applied on all the rows but produces single output.

a) SUM

This will give the sum of the values of the specified column.

Syntax: sum (column)

Ex:
SQL> select sum(sal) from emp;

SUM(SAL)


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----------
38600

b) AVG

This will give the average of the values of the specified column.

Syntax: avg (column)

Ex:
SQL> select avg(sal) from emp;

AVG(SAL)
---------------
2757.14286

c) MAX

This will give the maximum of the values of the specified column.

Syntax: max (column)

Ex:
SQL> select max(sal) from emp;

MAX(SAL)
----------
5000

d) MIN

This will give the minimum of the values of the specified column.

Syntax: min (column)

Ex:


70

SQL> select min(sal) from emp;

MIN(SAL)
----------
500

e) COUNT

This will give the count of the values of the specified column.

Syntax: count (column)

Ex:
SQL> select count(sal),count(*) from emp;

COUNT(SAL) COUNT(*)
-------------- ------------
14 14


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CONSTRAINTS

Constraints are categorized as follows.

Domain integrity constraints
 Not null
 Check

Entity integrity constraints
 Unique
 Primary key

Referential integrity constraints
 Foreign key

Constraints are always attached to a column not a table.
We can add constraints in three ways.

 Column level -- along with the column definition

 Table level -- after the table definition

 Alter level -- using alter command

While adding constraints you need not specify the name but the type only, oracle will
internally name the constraint.
If you want to give a name to the constraint, you have to use the constraint clause.

NOT NULL


72

This is used to avoid null values.
We can add this constraint in column level only.

Ex:
SQL> create table student(no number(2) not null, name varchar(10), marks
number(3));

SQL> create table student(no number(2) constraint nn not null, name varchar(10),
marks number(3));

CHECK

This is used to insert the values based on specified condition.
We can add this constraint in all three levels.

Ex:
COLUMN LEVEL

SQL> create table student(no number(2) , name varchar(10), marks number(3) check
(marks > 300));
SQL> create table student(no number(2) , name varchar(10), marks number(3)
constraint ch check(marks > 300));

TABLE LEVEL

SQL> create table student(no number(2) , name varchar(10), marks number(3), check
(marks > 300));
SQL> create table student(no number(2) , name varchar(10), marks number(3),
constraint ch check(marks > 300));

ALTER LEVEL

SQL> alter table student add check(marks>300);
SQL> alter table student add constraint ch check(marks>300);


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UNIQUE

This is used to avoid duplicates but it allow nulls.
We can add this constraint in all three levels.

Ex:
COLUMN LEVEL

SQL> create table student(no number(2) unique, name varchar(10), marks
number(3));
SQL> create table student(no number(2) constraint un unique, name varchar(10),
marks number(3));

TABLE LEVEL

unique(no));
constraint un unique(no));

ALTER LEVEL

SQL> alter table student add unique(no);
SQL> alter table student add constraint un unique(no);

PRIMARY KEY

 This is used to avoid duplicates and nulls. This will work as combination of unique
and not null.
 Primary key always attached to the parent table.

 We can add this constraint in all three levels.

Ex:


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COLUMN LEVEL

SQL> create table student(no number(2) primary key, name varchar(10), marks
number(3));
SQL> create table student(no number(2) constraint pk primary key, name varchar(10),
marks number(3));

TABLE LEVEL

primary key(no));
constraint pk primary key(no));

ALTER LEVEL

SQL> alter table student add primary key(no);
SQL> alter table student add constraint pk primary key(no);

FOREIGN KEY

 This is used to reference the parent table primary key column which allows
duplicates.
 Foreign key always attached to the child table.

 We can add this constraint in table and alter levels only.

Ex:
TABLE LEVEL

SQL> create table emp(empno number(2), ename varchar(10), deptno number(2),
primary key(empno), foreign key(deptno) references dept(deptno));
constraint pk primary key(empno), constraint fk foreign key(deptno) references
dept(deptno));


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ALTER LEVEL

SQL> alter table emp add foreign key(deptno) references dept(deptno);
SQL> alter table emp add constraint fk foreign key(deptno) references dept(deptno);

Once the primary key and foreign key relationship has been created then you can not
remove any parent record if the dependent childs exists.

USING ON DELTE CASCADE

By using this clause you can remove the parent record even it childs exists.
Because when ever you remove parent record oracle automatically removes all its
dependent records from child table, if this clause is present while creating foreign key
constraint.

Ex:
TABLE LEVEL

primary key(empno), foreign key(deptno) references dept(deptno) on delete
cascade);
constraint pk primary key(empno), constraint fk foreign key(deptno) references
dept(deptno) on delete cascade);

ALTER LEVEL

SQL> alter table emp add foreign key(deptno) references dept(deptno) on delete
cascade;
SQL> alter table emp add constraint fk foreign key(deptno) references dept(deptno) on
delete cascade;

COMPOSITE KEYS

A composite key can be defined on a combination of columns.
We can define composite keys on entity integrity and referential integrity constraints.


76

Composite key can be defined in table and alter levels only.

Ex:
UNIQUE (TABLE LEVEL)

unique(no,name));
constraint un unique(no,name));

UNIQUE (ALTER LEVEL)

SQL> alter table student add unique(no,name);
SQL> alter table student add constraint un unique(no,name);

PRIMARY KEY (TABLE LEVEL)

primary key(no,name));
constraint pk primary key(no,name));

PRIMARY KEY (ALTER LEVEL)

SQL> alter table student add primary key(no,anme);
SQL> alter table student add constraint pk primary key(no,name);

FOREIGN KEY (TABLE LEVEL)

dname varchar(10), primary key(empno), foreign key(deptno,dname) references
dept(deptno,dname));
dname varchar(10), constraint pk primary key(empno), constraint fk foreign
key(deptno,dname) references dept(deptno,dname));

FOREIGN KEY (ALTER LEVEL)


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SQL> alter table emp add foreign key(deptno,dname) references dept(deptno,dname);
SQL> alter table emp add constraint fk foreign key(deptno,dname) references
dept(deptno,dname);

DEFERRABLE CONSTRAINTS

Each constraint has two additional attributes to support deferred checking of constraints.
 Deferred initially immediate
 Deferred initially deferred
Deferred initially immediate checks for constraint violation at the time of insert.
Deferred initially deferred checks for constraint violation at the time of commit.

Ex:
SQL> create table student(no number(2), name varchar(10), marks number(3),
constraint un unique(no) deferred initially immediate);
SQL> create table student(no number(2), name varchar(10), marks number(3),
constraint un unique(no) deferred initially deferred);
SQL> alter table student add constraint un unique(no) deferrable initially deferred;

SQL> set constraints all immediate;
This will enable all the constraints violations at the time of inserting.

SQL> set constraints all deferred;
This will enable all the constraints violations at the time of commit.

OPERATIONS WITH CONSTRAINTS

Possible operations with constraints as follows.

 Enable

 Disable
 Enforce
 Drop

ENABLE


78

This will enable the constraint. Before enable, the constraint will check the existing data.

Ex:
SQL> alter table student enable constraint un;

DISABLE

This will disable the constraint.

Ex:
SQL> alter table student enable constraint un;

ENFORCE

This will enforce the constraint rather than enable for future inserts or updates.
This will not check for existing data while enforcing data.

Ex:
SQL> alter table student enforce constraint un;

DROP

This will remove the constraint.

Ex:
SQL> alter table student drop constraint un;
Once the table is dropped, constraints automatically will drop.


79

CASE AND DEFAULT

CASE

Case is similar to decode but easier to understand while going through coding

Ex:
SQL> Select sal,
Case sal
When 500 then ‘low’
When 5000 then ‘high’
Else ‘medium’
End case
From emp;

SAL CASE
----- --------
500 low
2500 medium
2000 medium
3500 medium
3000 medium
5000 high
4000 medium
5000 high
1800 medium


80

1200 medium
2000 medium
2700 medium
2200 medium
3200 medium

DEFAULT

Default can be considered as a substitute behavior of not null constraint when applied to
new rows being entered into the table.
When you define a column with the default keyword followed by a value, you are actually
telling the database that, on insert if a row was not assigned a value for this column, use
the default value that you have specified.
Default is applied only during insertion of new rows.

Ex:
SQL> create table student(no number(2) default 11,name varchar(2));
SQL> insert into student values(1,'a');
SQL> insert into student(name) values('b');


NO NAME
------ ---------
1 a
11 b

SQL> insert into student values(null, ‘c’);


NO NAME
------ ---------
1 a


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11 b
C
-- Default can not override nulls.

ABSTRACT DATA TYPES

Some times you may want type which holds all types of data including numbers, chars
and special characters something like this. You can not achieve this using pre-defined
types.
You can define custom types which holds your desired data.

Ex:
Suppose in a table we have address column which holds hno and city information.
We will define a custom type which holds both numeric as well as char data.

CREATING ADT

SQL> create type addr as object(hno number(3),city varchar(10)); /

CREATING TABLE BASED ON ADT

SQL> create table student(no number(2),name varchar(2),address addr);

INSERTING DATA INTO ADT TABLES

SQL> insert into student values(1,'a',addr(111,'hyd'));
SQL> insert into student values(2,'b',addr(222,'bang'));
SQL> insert into student values(3,'c',addr(333,'delhi'));

SELECTING DATA FROM ADT TABLES



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NO NAME ADDRESS(HNO, CITY)
--- ------- -------------------------
1 a ADDR(111, 'hyd')
2 b ADDR(222, 'bang')
3 c ADDR(333, 'delhi')

SQL> select no,name,s.address.hno,s.address.city from student s;

NO NAME ADDRESS.HNO ADDRESS.CITY
---- ------- ----------------- ----------------
1 a 111 hyd
2 b 222 bang
3 c 333 delhi

UPDATE WITH ADT TABLES

SQL> update student s set s.address.city = 'bombay' where s.address.hno = 333;

---- ------- ----------------- ----------------
1 a 111 hyd
2 b 222 bang
3 c 333 bombay

DELETE WITH ADT TABLES

SQL> delete student s where s.address.hno = 111;

---- ------- ----------------- ----------------
2 b 222 bang
3 c 333 bombay

DROPPING ADT


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SQL> drop type addr;

OBJECT VIEWS AND METHODS

OBJECT VIEWS

If you want to implement objects with the existing table, object views come into picture.
You define the object and create a view which relates this object to the existing table
nothing but object view.

Object views are used to relate the user defined objects to the existing table.

Ex:
1) Assume that the table student has already been created with the following columns
SQL> create table student(no number(2),name varchar(10),hno number(3),city
varchar(10));
2) Create the following types
SQL> create type addr as object(hno number(2),city varchar(10));/
SQL> create type stud as object(name varchar(10),address addr);/
3) Relate the objects to the student table by creating the object view
SQL> create view student_ov(no,stud_info) as select no,stud(name,addr(hno,city))
from student;
4) Now you can insert data into student table in two ways
a) By regular insert
SQL> Insert into student values(1,’sudha’,111,’hyd’);
b) By using object view
SQL> Insert into student_ov values(1,stud(‘sudha’,addr(111,’hyd’)));

METHODS


84

You can define methods which are nothing but functions in types and apply in the tables
which holds the types;

Ex:
1) Defining methods in types
SQL> Create type stud as object(name varchar(10),marks number(3),
Member function makrs_f(marks in number) return number,
Pragma restrict_references(marks_f,wnds,rnds,wnps,fnps));/
2) Defining type body
SQL> Create type body stud as
Member function marks_f(marks in number) return number is
Begin
Return (marks+100);
End marks_f;
End;/
3) Create a table using stud type
SQL> Create table student(no number(2),info stud);
4) Insert some data into student table
SQL> Insert into student values(1,stud(‘sudha’,100));
5) Using method in select
SQL> Select s.info.marks_f(s.info.marks) from student s;
-- Here we are using the pragma restrict_references to avoid the writes to the
Database.


85

VARRAYS AND NESTED TABLES

VARRAYS

A varying array allows you to store repeating attributes of a record in a single row but
with limit.

Ex:
1) We can create varrays using oracle types as well as user defined types.
a) Varray using pre-defined types
SQL> Create type va as varray(5) of varchar(10);/
b) Varrays using user defined types
SQL> Create type addr as object(hno number(3),city varchar(10));/
SQL> Create type va as varray(5) of addr;/
2) Using varray in table
SQL> Create table student(no number(2),name varchar(10),address va);
3) Inserting values into varray table
SQL> Insert into student values(1,’sudha’,va(addr(111,’hyd’)));
SQL> Insert into student values(2,’jagan’,va(addr(111,’hyd’),addr(222,’bang’)));
4) Selecting data from varray table
SQL> Select * from student;
-- This will display varray column data along with varray and adt;
SQL> Select no,name, s.* from student s1, table(s1.address) s;
-- This will display in general format
5) Instead of s.* you can specify the columns in varray
SQL> Select no,name, s.hno,s.city from student s1,table(s1.address) s;

-- Update and delete not possible in varrays.


86

-- Here we used table function which will take the varray column as input for producing
output excluding varray and types.

NESTED TABLES

A nested table is, as its name implies, a table within a table. In this case it is a table that
is represented as a column within another table.
Nested table has the same effect of varrays but has no limit.

Ex:
1) We can create nested tables using oracle types and user defined types which has no
limit.
a) Nested tables using pre-defined types
SQL> Create type nt as table of varchar(10);/
b) Nested tables using user defined types
SQL> Create type addr as object(hno number(3),city varchar(10));/
SQL> Create type nt as table of addr;/
2) Using nested table in table
SQL> Create table student(no number(2),name varchar(10),address nt) nested table
address store as student_temp;
3) Inserting values into table which has nested table
SQL> Insert into student values (1,’sudha’,nt(addr(111,’hyd’)));
SQL> Insert into student values (2,’jagan’,nt(addr(111,’hyd’),addr(222,’bang’)));
4) Selecting data from table which has nested table
SQL> Select * from student;
-- This will display nested table column data along with nested table and adt;
SQL> Select no,name, s.* from student s1, table(s1.address) s;
-- This will display in general format
5) Instead of s.* you can specify the columns in nested table
SQL> Select no,name, s.hno,s.city from student s1,table(s1.address) s;
6) Inserting nested table data to the existing row
SQL> Insert into table(select address from student where no=1)


87

values(addr(555,’chennai’));
7) Update in nested tables
SQL> Update table(select address from student where no=2) s set s.city=’bombay’
where s.hno = 222;
8) Delete in nested table
SQL> Delete table(select address from student where no=3) s where s.hno=333;

DATA MODEL

 ALL_COLL_TYPES
 ALL_TYPES
 DBA_COLL_TYPES
 DBA_TYPES
 USER_COLL_TYPES
 USER_TYPES


88

FLASHBACK QUERY

Used to retrieve the data which has been already committed with out going for recovery.

Flashbacks are of two types
 Time base flashback
 SCN based flashback (SCN stands for System Change Number)

Ex:

1) Using time based flashback
a) SQL> Select *from student;
-- This will display all the rows
b) SQL> Delete student;
c) SQL> Commit; -- this will commit the work.
d) SQL> Select *from student;
-- Here it will display nothing
e) Then execute the following procedures
SQL> Exec dbms_flashback.enable_at_time(sysdate-2/1440)
f) SQL> Select *from student;
-- Here it will display the lost data
-- The lost data will come but the current system time was used
g) SQL> Exec dbms_flashback.disable
-- Here we have to disable the flashback to enable it again

2) Using SCN based flashback
a) Declare a variable to store SCN
SQL> Variable s number


89

b) Get the SCN
SQL> Exec :s := exec dbms_flashback.get_system_change_number
c) To see the SCN
SQL> Print s
d) Then execute the following procedures
SQL> Exec dbms_flashback.enable_at_system_change_number(:s)
SQL> Exec dbms_flashback.disable

EXTERNAL TABLES

You can user external table feature to access external files as if they are tables inside the
database.
When you create an external table, you define its structure and location with in oracle.
When you query the table, oracle reads the external table and returns the results just as
if the data had been stored with in the database.

ACCESSING EXTERNAL TABLE DATA

To access external files from within oracle, you must first use the create directory
command to define a directory object pointing to the external file location
Users who will access the external files must have the read and write privilege on the
directory.

Ex:

CREATING DIRECTORY AND OS LEVEL FILE

SQL> Sqlplus system/manager
SQL> Create directory saketh_dir as ‘/Visdb/visdb/9.2.0/external’;
SQL> Grant all on directory saketh_dir to saketh;
SQL> Conn saketh/saketh
SQL> Spool dept.lst
SQL> Select deptno || ‘,’ || dname || ‘,’ || loc from dept;
SQL> Spool off

CREATING EXTERNAL TABLE


90

SQL> Create table dept_ext
(deptno number(2),
Dname varchar(14),
Loc varchar(13))
Organization external ( type oracle_loader
Default directory saketh_dir
Access parameters
( records delimited by newline
Fields terminated by “,”
( deptno number(2),
Dname varchar(14),
Loc varchar(13)))
Location (‘/Visdb/visdb/9.2.0/dept.lst’));

SELECTING DATA FROM EXTERNAL TABLE

SQL> select * from dept_ext;
This will read from dept.lst which is a operating system level file.

LIMITATIONS ON EXTERNAL TABLES

a) You can not perform insert, update, and delete operations
a) Indexing not possible
b) Constraints not possible

BENEFITS OF EXTERNAL TABLES

a) Queries of external tables complete very quickly even though a full table scan id
required with each access
b) You can join external tables to each other or to standard tables


91

REF DEREF VALUE

REF

 The ref function allows referencing of existing row objects.
 Each of the row objects has an object id value assigned to it.
 The object id assigned can be seen by using ref function.

DEREF

 The deref function performs opposite action.
 It takes a reference value of object id and returns the value of the row objects.

VALUE

 Even though the primary table is object table, still it displays the rows in general
format.
 To display the entire structure of the object, this will be used.

Ex:
1) create vendot_adt type
SQL> Create type vendor_adt as object (vendor_code number(2), vendor_name
varchar(2), vendor_address varchar(10));/
2) create object tables vendors and vendors1
SQL> Create table vendors of vendor_adt;
SQL> Create table vendors1 of vendor_adt;
3) insert the data into object tables
SQL> insert into vendors values(1, ‘a’, ‘hyd’);


92

SQL> insert into vendors values(2, ‘b’, ‘bang’);
SQL> insert into vendors1 values(3, ‘c’, ‘delhi’);
SQL> insert into vendors1 values(4, ‘d’, ‘chennai’);
4) create another table orders which holds the vendor_adt type also.
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt);
Or

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt with
rowid);
5) insert the data into orders table
The vendor_info column in the following syntaxes will store object id of any table
which is referenced by vendor_adt object ( both vendors and vendors1).
SQL> insert into orders values(11,(select ref(v) from vendors v where vendor_code
= 1));
SQL> insert into orders values(12,(select ref(v) from vendors v where vendor_code
= 2));
SQL> insert into orders values(13,(select ref(v1) from vendors1 v1 where
vendor_code = 1));
SQL> insert into orders values(14,(select ref(v1) from vendors1 v1 where
vendor_code = 1));
6) To see the object ids of vendor table
SQL> Select ref(V) from vendors v;
7) If you see the vendor_info of orders it will show only the object ids not the values,
to see the values
SQL> Select deref(o.vendor_info) from orders o;
8) Even though the vendors table is object table it will not show the adt along with
data, to see the data along with the adt
SQL>Select * from vendors;
This will give the data without adt.
SQL>Select value(v) from vendors v;
This will give the columns data along wih the type.

REF CONSTRAINTS

 Ref can also acts as constraint.


93

 Even though vendors1 also holding vendor_adt, the orders table will store the
object ids of vendors only because it is constrained to that table only.

 The vendor_info column in the following syntaxes will store object ids of
vendors only.

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt scope is
vendors);
Or
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt constraint fk
references vendors);


94

OBJECT VIEWS WITH REFERENCES

To implement the objects and the ref constraints to the existing tables, what we can do?
Simply drop the both tables and recreate with objects and ref constrains.

But you can achieve this with out dropping the tables and without losing the data by
creating object views with references.

Ex:
a) Create the following tables
SQL> Create table student1(no number(2) primary key,name varchar(2),marks
number(3));
SQL> Create table student2(no number(2) primary key,hno number(3),city
varchar(10),id number(2),foreign Key(id) references student1(no));
b) Insert the records into both tables
SQL> insert into student1(1,’a’,100);
SQL> insert into student1(2,’b’,200);
SQL> insert into student2(11,111,’hyd’,1);
SQL> insert into student2(12,222,’bang’,2);
SQL> insert into student2(13,333,’bombay’,1);
c) Create the type
SQL> create or replace type stud as object(no number(2),name varchar(2),marks
number(3));/
d) Generating OIDs
SQL> Create or replace view student1_ov of stud with object identifier(or id) (no) as
Select * from Student1;
e) Generating references
SQL> Create or replace view student2_ov as select no,hno,city,


95

make_ref(student1_ov,id) id from Student2;
d) Query the following
SQL> select *from student1_ov;
SQL> select ref(s) from student1_ov s;
SQL> select values(s) from student1_ov;
SQ> select *from student2_ov;
SQL> select deref(s.id) from student2_ov s;

PARTITIONS

A single logical table can be split into a number of physically separate pieces based on
ranges of key values. Each of the parts of the table is called a partition.
A non-partitioned table can not be partitioned later.

TYPES

 Range partitions
 List partitions
 Hash partitions
 Sub partitions

ADVANTAGES

 Reducing downtime for scheduled maintenance, which allows maintenance
operations to be carried out on selected partitions while other partitions are
available to users.
 Reducing downtime due to data failure, failure of a particular partition will no way
affect other partitions.
 Partition independence allows for concurrent use of the various partitions for
various purposes.

ADVANTAGES OF PARTITIONS BY STORING THEM IN DIFFERENT TABLESPACES

 Reduces the possibility of data corruption in multiple partitions.
 Back up and recovery of each partition can be done independently.


96

DISADVANTAGES

 Partitioned tables cannot contain any columns with long or long raw datatypes,
LOB types or object types.

RANGE PARTITIONS

a) Creating range partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by range(no)
(partition p1 values less than(10), partition p2 values less than(20), partition p3
values less than(30),partition p4 values less than(maxvalue));

** if you are using maxvalue for the last partition, you can not add a partition.
b) Inserting records into range partitioned table
SQL> Insert into student values(1,’a’); -- this will go to p1
SQL> Insert into student values(11,’b’); -- this will go to p2
SQL> Insert into student values(21,’c’); -- this will go to p3
SQL> Insert into student values(31,’d’); -- this will go to p4
c) Retrieving records from range partitioned table
SQL> Select *from student;
SQL> Select *from student partition(p1);
d) Possible operations with range partitions
 Add
 Drop
 Truncate
 Rename
 Split
 Move
 Exchange
e) Adding a partition
SQL> Alter table student add partition p5 values less than(40);
f) Dropping a partition
SQL> Alter table student drop partition p4;


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g) Renaming a partition
SQL> Alter table student rename partition p3 to p6;
h) Truncate a partition
SQL> Alter table student truncate partition p6;
i) Splitting a partition
SQL> Alter table student split partition p2 at(15) into (partition p21,partition p22);

j) Exchanging a partition
SQL> Alter table student exchange partition p1 with table student2;
k) Moving a partition
SQL> Alter table student move partition p21 tablespace saketh_ts;

LIST PARTITIONS

a) Creating list partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by list(no)
(partition p1 values(1,2,3,4,5), partition p2 values(6,7,8,9,10),partition p3
values(11,12,13,14,15), partition p4 values(16,17,18,19,20));
b) Inserting records into list partitioned table
SQL> Insert into student values(11,’c’); -- this will go to p3
SQL> Insert into student values(16,’d’); -- this will go to p4
c) Retrieving records from list partitioned table
d) Possible operations with list partitions
 Add
 Drop
 Truncate
 Rename
 Move
 Exchange
SQL> Alter table student add partition p5 values(21,22,23,24,25);


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i) Exchanging a partition
SQL> Alter table student exchange partition p1 with table student2;
j) Moving a partition
SQL> Alter table student move partition p2 tablespace saketh_ts;

HASH PARTITIONS

a) Creating hash partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by hash(no)
partitions 5;
Here oracle automatically gives partition names like
SYS_P1
SYS_P2
SYS_P3
SYS_P4
SYS_P5
b) Inserting records into hash partitioned table
it will insert the records based on hash function calculated by taking the partition key
SQL> Insert into student values(1,’a’);
SQL> Insert into student values(6,’b’);
SQL> Insert into student values(11,’c’);
SQL> Insert into student values(16,’d’);
c) Retrieving records from hash partitioned table
SQL> Select *from student partition(sys_p1);
d) Possible operations with hash partitions
 Add
 Truncate


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 Rename
 Move
 Exchange
SQL> Alter table student add partition p6 ;
f) Renaming a partition
g) Truncate a partition
h) Exchanging a partition
SQL> Alter table student exchange partition sys_p1 with table student2;
i) Moving a partition
SQL> Alter table student move partition sys_p2 tablespace saketh_ts;

SUB-PARTITIONS WITH RANGE AND HASH

Subpartitions clause is used by hash only. We can not create subpartitions with list and
hash partitions.

a) Creating subpartitioned table
SQL> Create table student(no number(2),name varchar(2),marks number(3))
Partition by range(no) subpartition by hash(name) subpartitions 3
(Partition p1 values less than(10),partition p2 values less than(20));

This will create two partitions p1 and p2 with three subpartitions for each partition
P1 – SYS_SUBP1
SYS_SUBP2
SYS_SUBP3
P2 – SYS_SUBP4
SYS_SUBP5
SYS_SUBP6
** if you are using maxvalue for the last partition, you can not add a partition.
b) Inserting records into subpartitioned table
c) Retrieving records from subpartitioned table


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SQL> Select *from student subpartition(sys_subp1);
d) Possible operations with subpartitions
 Add
 Drop
 Truncate
 Rename
 Split
SQL> Alter table student add partition p3 values less than(30);
i) Splitting a partition
SQL> Alter table student split partition p3 at(15) into (partition p31,partition p32);

DATA MODEL

 ALL_IND_PARTITIONS
 ALL_IND_SUBPARTITIONS
 ALL_TAB_PARTITIONS
 ALL_TAB_SUBPARTITIONS
 DBA_IND_PARTITIONS
 DBA_IND_SUBPARTITIONS
 DBA_TAB_PARTITIONS
 DBA_TAB_SUBPARTITIONS
 USER_IND_PARTITIONS
 USER_IND_SUBPARTITIONS
 USER_TAB_PARTITIONS
 USER_TAB_SUBPARTITIONS


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GROUP BY AND HAVING

GROUP BY

Using group by, we can create groups of related information.
Columns used in select must be used with group by, otherwise it was not a group by
expression.

Ex:
SQL> select deptno, sum(sal) from emp group by deptno;

DEPTNO SUM(SAL)
---------- ----------
10 8750
20 10875
30 9400

SQL> select deptno,job,sum(sal) from emp group by deptno,job;

DEPTNO JOB SUM(SAL)
---------- --------- ----------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975


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30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600

HAVING

This will work as where clause which can be used only with group by because of absence
of where clause in group by.
Ex:
SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) >
3000;

DEPTNO JOB TSAL
---------- --------- ----------
10 PRESIDENT 5000
20 ANALYST 6000
30 SALESMAN 5600

SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) >
3000 order by job;

DEPTNO JOB TSAL
---------- --------- ----------
20 ANALYST 6000
10 PRESIDENT 5000
30 SALESMAN 5600

ORDER OF EXECUTION

 Group the rows together based on group by clause.
 Calculate the group functions for each group.
 Choose and eliminate the groups based on the having clause.
 Order the groups based on the specified column.


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ROLLUP GROUPING CUBE

These are the enhancements to the group by feature.

USING ROLLUP

This will give the salaries in each department in each job category along wih the total
salary for individual departments and the total salary of all the departments.

SQL> Select deptno,job,sum(sal) from emp group by rollup(deptno,job);

DEPTNO JOB SUM(SAL)
---------- --------- ----------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 9400
29025


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USING GROUPING

In the above query it will give the total salary of the individual departments but with a
blank in the job column and gives the total salary of all the departments with blanks in
deptno and job columns.

To replace these blanks with your desired string grouping will be used

SQL> select decode(grouping(deptno),1,'All Depts',deptno),decode(grouping(job),1,'All
jobs',job),sum(sal) from emp group by rollup(deptno,job);

DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)
----------------------------------- ---------------------------------- --------------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 All jobs 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 All jobs 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 All jobs 9400
All Depts All jobs 29025

Grouping will return 1 if the column which is specified in the grouping function has been
used in rollup.
Grouping will be used in association with decode.

USING CUBE


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This will give the salaries in each department in each job category, the total salary for
individual departments, the total salary of all the departments and the salaries in each job
category.

SQL> select decode(grouping(deptno),1,’All Depts’,deptno),decode(grouping(job),1,’All
Jobs’,job),sum(sal) from emp group by cube(deptno,job);

DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)
----------------------------------- ------------------------------------ ------------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 All Jobs 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 All Jobs 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 All Jobs 9400
All Depts ANALYST 6000
All Depts CLERK 4150
All Depts MANAGER 8275
All Depts PRESIDENT 5000
All Depts SALESMAN 5600
All Depts All Jobs 29025


106

SET OPERATORS

TYPES

 Union
 Union all
 Intersect
 Minus

UNION

This will combine the records of multiple tables having the same structure.

Ex:
SQL> select * from student1 union select * from student2;

UNION ALL

This will combine the records of multiple tables having the same structure but including
duplicates.

Ex:
SQL> select * from student1 union all select * from student2;

INTERSECT


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This will give the common records of multiple tables having the same structure.

Ex:
SQL> select * from student1 intersect select * from student2;

MINUS

This will give the records of a table whose records are not in other tables having the same
structure.

Ex:
SQL> select * from student1 minus select * from student2;


108

VIEWS

A view is a database object that is a logical representation of a table. It is delivered from
a table but has no storage of its own and often may be used in the same manner as a
table.

A view takes the output of the query and treats it as a table, therefore a view can be
thought of as a stored query or a virtual table.

TYPES
 Simple view
 Complex view

Simple view can be created from one table where as complex view can be created from
multiple tables.

WHY VIEWS?

 Provides additional level of security by restricting access to a predetermined set of
rows and/or columns of a table.
 Hide the data complexity.
 Simplify commands for the user.

VIEWS WITHOUT DML


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 Read only view
 View with group by
 View with aggregate functions
 View with rownum
 Partition view
 View with distinct

Ex:
SQL> Create view dept_v as select *from dept with read only;
SQL> Create view dept_v as select deptno, sum(sal) t_sal from emp group by deptno;
SQL> Create view stud as select rownum no, name, marks from student;
SQL> Create view student as select *from student1 union select *from student2;
SQL> Create view stud as select distinct no,name from student;

VIEWS WITH DML

 View with not null column -- insert with out not null column not possible
-- update not null column to null is not possible
-- delete possible

 View with out not null column which was in base table -- insert not possible
-- update, delete possible

 View with expression -- insert , update not possible
-- delete possible

 View with functions (except aggregate) -- insert, update not possible
-- delete possible

 View was created but the underlying table was dropped then we will get the
message like “ view has errors ”.

 View was created but the base table has been altered but still the view was with
the initial definition, we have to replace the view to affect the changes.

 Complex view (view with more than one table) -- insert not possible
-- update, delete possible (not always)

CREATING VIEW WITHOUT HAVING THE BASE TABLE


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SQL> Create force view stud as select *From student;
-- Once the base table was created then the view is validated.

VIEW WITH CHECK OPTION CONSTRAINT

SQL> Create view stud as select *from student where marks = 500 with check option
constraint Ck;
- Insert possible with marks value as 500
- Update possible excluding marks column
- Delete possible

DROPPING VIEWS

SQL> drop view dept_v;

DATA MODEL

ALL_VIEW
DBA_VIEW
USER_VIEWS


111

SYNONYM AND SEQUENCE

SYNONYM

A synonym is a database object, which is used as an alias for a table, view or sequence.

TYPES

 Private
 Public
Private synonym is available to the particular user who creates.
Public synonym is created by DBA which is available to all the users.

ADVANTAGES

 Hide the name and owner of the object.
 Provides location transparency for remote objects of a distributed database.

CREATE AND DROP

SQL> create synonym s1 for emp;
SQL> create public synonym s2 for emp;
SQL> drop synonym s1;

SEQUENCE


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A sequence is a database object, which can generate unique, sequential integer values.
It can be used to automatically generate primary key or unique key values.
A sequence can be either in an ascending or descending order.

Syntax:
Create sequence <seq_name> [increment bty n] [start with n] [maxvalue n]
[minvalue n] [cycle/nocycle] [cache/nocache];

By defalult the sequence starts with 1, increments by 1 with minvalue of 1 and with
nocycle, nocache.
Cache option pre-alloocates a set of sequence numbers and retains them in memory for
faster access.

Ex:
SQL> create sequence s;
SQL> create sequence s increment by 10 start with 100 minvalue 5 maxvalue 200 cycle
cache 20;

USING SEQUENCE

SQL> create table student(no number(2),name varchar(10));
SQL> insert into student values(s.nextval, ‘saketh’);

 Initially currval is not defined and nextval is starting value.
 After that nextval and currval are always equal.

CREATING ALPHA-NUMERIC SEQUENCE

SQL> create sequence s start with 111234;
SQL> Insert into student values (s.nextval || translate
(s.nextval,’1234567890’,’abcdefghij’));

ALTERING SEQUENCE

We can alter the sequence to perform the following.

 Set or eliminate minvalue or maxvalue.


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 Change the increment value.
 Change the number of cached sequence numbers.

Ex:
SQL> alter sequence s minvalue 5;
SQL> alter sequence s increment by 2;
SQL> alter sequence s cache 10;

DROPPING SEQUENCE

SQL> drop sequence s;

JOINS

 The purpose of a join is to combine the data across tables.
 A join is actually performed by the where clause which combines the specified rows
of tables.
 If a join involves in more than two tables then oracle joins first two tables based on
the joins condition and then compares the result with the next table and so on.

TYPES
• Equi join
• Non-equi join
• Self join
• Natural join
• Cross join
• Outer join
 Left outer
 Right outer
 Full outer
• Inner join
• Using clause
• On clause

Assume that we have the following tables.


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SQL> select * from dept;

DEPTNO DNAME LOC
------ ---------- ----------
10 mkt hyd
20 fin bang
30 hr bombay

SQL> select * from emp;

EMPNO ENAME JOB MGR DEPTNO
---------- ---------- ---------- ---------- ----------
111 saketh analyst 444 10
222 sudha clerk 333 20
333 jagan manager 111 10
444 madhu engineer 222 40

EQUI JOIN

A join which contains an ‘=’ operator in the joins condition.

Ex:
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno=d.deptno;

EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang

USING CLAUSE


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SQL> select empno,ename,job ,dname,loc from emp e join dept d using(deptno);

---------- ---------- ---------- ---------- ----------

ON CLAUSE

SQL> select empno,ename,job,dname,loc from emp e join dept d on(e.deptno=d.deptno);
---------- ---------- ---------- ---------- ----------

NON-EQUI JOIN

A join which contains an operator other than ‘=’ in the joins condition.

Ex:
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno >
d.deptno;

---------- ---------- ---------- ---------- ----------
222 sudha clerk mkt hyd
444 madhu engineer mkt hyd
444 madhu engineer fin bang
444 madhu engineer hr bombay

SELF JOIN

Joining the table itself is called self join.


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Ex:
SQL> select e1.empno,e2.ename,e1.job,e2.deptno from emp e1,emp e2 where
e1.empno=e2.mgr;

EMPNO ENAME JOB DEPTNO
---------- ---------- ---------- ----------
111 jagan analyst 10
222 madhu clerk 40
333 sudha manager 20
444 saketh engineer 10
NATURAL JOIN

Natural join compares all the common columns.

Ex:
SQL> select empno,ename,job,dname,loc from emp natural join dept;

---------- ---------- ---------- ---------- ----------

CROSS JOIN

This will gives the cross product.

Ex:
SQL> select empno,ename,job,dname,loc from emp cross join dept;

---------- ---------- ---------- ---------- ----------
222 sudha clerk mkt hyd


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444 madhu engineer mkt hyd
111 saketh analyst fin bang
333 jagan manager fin bang
444 madhu engineer fin bang
111 saketh analyst hr bombay
222 sudha clerk hr bombay
333 jagan manager hr bombay
444 madhu engineer hr bombay

OUTER JOIN

Outer join gives the non-matching records along with matching records.

LEFT OUTER JOIN

This will display the all matching records and the records which are in left hand side table
those that are not in right hand side table.

Ex:
SQL> select empno,ename,job,dname,loc from emp e left outer join dept d
on(e.deptno=d.deptno);
Or
SQL> select empno,ename,job,dname,loc from emp e,dept d where
e.deptno=d.deptno(+);

---------- ---------- ---------- ---------- ----------
444 madhu engineer

RIGHT OUTER JOIN


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This will display the all matching records and the records which are in right hand side
table those that are not in left hand side table.

Ex:
SQL> select empno,ename,job,dname,loc from emp e right outer join dept d
Or
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno(+) =
d.deptno;

---------- ---------- ---------- ---------- ----------
hr bombay

FULL OUTER JOIN

This will display the all matching records and the non-matching records from both tables.

Ex:
SQL> select empno,ename,job,dname,loc from emp e full outer join dept d

---------- ---------- ---------- ---------- ----------
444 madhu engineer
hr bombay

INNER JOIN

This will display all the records that have matched.


119

Ex:
SQL> select empno,ename,job,dname,loc from emp inner join dept using(deptno);

---------- ---------- ---------- ---------- ----------

SUBQUERIES AND EXISTS

SUBQUERIES

 Nesting of queries, one within the other is termed as a subquery.
 A statement containing a subquery is called a parent query.
 Subqueries are used to retrieve data from tables that depend on the values in the
table itself.

TYPES

 Single row subqueries
 Multi row subqueries
 Multiple subqueries

 Correlated subqueries

SINGLE ROW SUBQUERIES

In single row subquery, it will return one value.

Ex:
SQL> select * from emp where sal > (select sal from emp where empno = 7566);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO


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---------- ---------- --------- ---------- ------------ ------- ---------- ----------
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7902 FORD ANALYST 7566 03-DEC-81 3000 20

MULTI ROW SUBQUERIES

In multi row subquery, it will return more than one value. In such cases we should
include operators like any, all, in or not in between the comparision operator and the
subquery.

Ex:
SQL> select * from emp where sal > any (select sal from emp where sal between 2500
and 4000);

---------- ---------- --------- ---------- ----------- -------- ---------- ----------
7566 JONES MANAGER 7839 02-APR-81 2975 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20

SQL> select * from emp where sal > all (select sal from emp where sal between 2500
and 4000);

---------- ---------- --------- ---------- ------------- ------ ---------- ----------

MULTIPLE SUBQUERIES

There is no limit on the number of subqueries included in a where clause. It allows
nesting of a query within a subquery.

Ex:
SQL> select * from emp where sal = (select max(sal) from emp where sal < (select


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max(sal) from emp));

---------- ---------- --------- ---------- ------------ ------- ---------- ----------
7902 FORD ANALYST 7566 03-DEC-81 3000 20

CORRELATED SUBQUERIES

A subquery is evaluated once for the entire parent statement where as a correlated
subquery is evaluated once for every row processed by the parent statement.
Ex:
SQL> select distinct deptno from emp e where 5 <= (select count(ename) from emp
where e.deptno = deptno);

DEPTNO
----------
20
30

EXISTS

Exists function is a test for existence. This is a logical test for the return of rows from a
query.

Ex:
Suppose we want to display the department numbers which has more than 4
employees.

SQL> select deptno,count(*) from emp group by deptno having count(*) > 4;

DEPTNO COUNT(*)
--------- ----------
20 5
30 6


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From the above query can you want to display the names of employees?
SQL> select deptno,ename, count(*) from emp group by deptno,ename having count(*)
> 4;

no rows selected

The above query returns nothing because combination of deptno and ename never
return more than one count.

The solution is to use exists which follows.

SQL> select deptno,ename from emp e1 where exists (select * from emp e2
where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4)
order by deptno,ename;

DEPTNO ENAME
---------- ----------
20 ADAMS
20 FORD
20 JONES
20 SCOTT
20 SMITH
30 ALLEN
30 BLAKE
30 JAMES
30 MARTIN
30 TURNER
30 WARD

NOT EXISTS

SQL> select deptno,ename from emp e1 where not exists (select * from emp e2
where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4) order
by deptno,ename;

DEPTNO ENAME


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--------- ----------
10 CLARK
10 KING
10 MILLER

WALKUP TREES AND INLINE VIEW

WALKUP TREES

Using hierarchical queries, you can retrieve data based on a natural hierarchical
relationship between rows in a table. However, where a hierarchical relationship exists
between the rows of a table, a process called tree walking enables the hierarchy to be
constructed.

Ex:
SQL> select ename || '==>' || prior ename, level from emp start with ename = 'KING'
connect by prior empno=mgr;

ENAME||'==>'||PRIORENAM LEVEL
------------------------------------ --------
KING==> 1
JONES==>KING 2
SCOTT==>JONES 3
ADAMS==>SCOTT 4
FORD==>JONES 3
SMITH==>FORD 4
BLAKE==>KING 2
ALLEN==>BLAKE 3
WARD==>BLAKE 3


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MARTIN==>BLAKE 3
TURNER==>BLAKE 3
JAMES==>BLAKE 3
CLARK==>KING 2
MILLER==>CLARK 3

In the above
Start with clause specifies the root row of the table.
Level pseudo column gives the 1 for root , 2 for child and so on.
Connect by prior clause specifies the columns which has parent-child relationship.

INLINE VIEW OR TOP-N ANALYSIS

In the select statement instead of table name, replacing the select statement is known as
inline view.

Ex:
SQL> Select ename, sal, rownum rank from (select *from emp order by sal);

ENAME SAL RANK
---------- ---------- ----------
SMITH 800 1
JAMES 950 2
ADAMS 1100 3
WARD 1250 4
MARTIN 1250 5
MILLER 1300 6
TURNER 1500 7
ALLEN 1600 8
CLARK 2450 9
BLAKE 2850 10
JONES 2975 11
SCOTT 3000 12
FORD 3000 13
KING 5000 14


125

LOCKS

Locks are the mechanisms used to prevent destructive interaction between users
accessing same resource simultaneously. Locks provides high degree of data concurrency.

TYPES
 Row level locks
 Table level locks

ROW LEVEL LOCKS

In the row level lock a row is locked exclusively so that other cannot modify the row until
the transaction holding the lock is committed or rolled back. This can be done by using
select..for update clause.

Ex:
SQL> select * from emp where sal > 3000 for update of comm.;

TABLE LEVEL LOCKS

A table level lock will protect table data thereby guaranteeing data integrity when data is
being accessed concurrently by multiple users. A table lock can be held in several modes.


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 Share lock
 Share update lock
 Exclusive lock

SHARE LOCK

A share lock locks the table allowing other users to only query but not insert, update or
delete rows in a table. Multiple users can place share locks on the same resource at the
same time.

Ex:
SQL> lock table emp in share mode;
SHARE UPDATE LOCK

It locks rows that are to be updated in a table. It permits other users to concurrently
query, insert , update or even lock other rows in the same table. It prevents the other
users from updating the row that has been locked.

Ex:
SQL> lock table emp in share update mode;

EXCLUSIVE LOCK

Exclusive lock is the most restrictive of tables locks. When issued by any user, it allows
the other user to only query. It is similar to share lock but only one user can place
exclusive lock on a table at a time.

Ex:
SQL> lock table emp in share exclusive mode;

NOWAIT

If one user locked the table without nowait then another user trying to lock the same
table then he has to wait until the user who has initially locked the table issues a commit
or rollback statement. This delay could be avoided by appending a nowait clause in the
lock table command.


127

Ex:
SQL> lock table emp in exclusive mode nowait.

DEADLOCK

A deadlock occurs when tow users have a lock each on separate object, and they want to
acquire a lock on the each other’s object. When this happens, the first user has to wait for
the second user to release the lock, but the second user will not release it until the lock
on the first user’s object is freed. In such a case, oracle detects the deadlock
automatically and solves the problem by aborting one of the two transactions.

INDEXES

Index is typically a listing of keywords accompanied by the location of information on a
subject. We can create indexes explicitly to speed up SQL statement execution on a table.
The index points directly to the location of the rows containing the value.

WHY INDEXES?

Indexes are most useful on larger tables, on columns that are likely to appear in where
clauses as simple equality.

TYPES

 Unique index
 Non-unique index
 Btree index
 Bitmap index
 Composite index
 Reverse key index
 Function-based index
 Descending index
 Domain index


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 Object index
 Cluster index
 Text index
 Index organized table
 Partition index
 Local index
 Local prefixed
 Local non-prefixed
 Global index
 Global prefixed
 Global non-prefixed

UNIQUE INDEX

Unique indexes guarantee that no two rows of a table have duplicate values in the
columns that define the index. Unique index is automatically created when primary key or
unique constraint is created.

Ex:
SQL> create unique index stud_ind on student(sno);

NON-UNIQUE INDEX

Non-Unique indexes do not impose the above restriction on the column values.

Ex:
SQL> create index stud_ind on student(sno);

BTREE INDEX or ASCENDING INDEX

The default type of index used in an oracle database is the btree index. A btree index is
designed to provide both rapid access to individual rows and quick access to groups of
rows within a range. The btree index does this by performing a succession of value
comparisons. Each comparison eliminates many of the rows.


129

Ex:
SQL> create index stud_ind on student(sno);

BITMAP INDEX

This can be used for low cardinality columns: that is columns in which the number of
distinct values is snall when compared to the number of the rows in the table.

Ex:
SQL> create bitmap index stud_ind on student(sex);

COMPOSITE INDEX

A composite index also called a concatenated index is an index created on multiple
columns of a table. Columns in a composite index can appear in any order and need not be
adjacent columns of the table.

Ex:
SQL> create bitmap index stud_ind on student(sno, sname);

REVERSE KEY INDEX

A reverse key index when compared to standard index, reverses each byte of the column
being indexed while keeping the column order. When the column is indexed in reverse
mode then the column values will be stored in an index in different blocks as the starting
value differs. Such an arrangement can help avoid performance degradations in indexes
where modifications to the index are concentrated on a small set of blocks.

Ex:
SQL> create index stud_ind on student(sno, reverse);

We can rebuild a reverse key index into normal index using the noreverse keyword.

Ex:


130

SQL> alter index stud_ind rebuild noreverse;

FUNCTION BASED INDEX

This will use result of the function as key instead of using column as the value for the key.

Ex:
SQL> create index stud_ind on student(upper(sname));

DESCENDING INDEX

The order used by B-tree indexes has been ascending order. You can categorize data in B-
tree index in descending order as well. This feature can be useful in applications where
sorting operations are required.

Ex:
SQL> create index stud_ind on student(sno desc);

TEXT INDEX

Querying text is different from querying data because words have shades of meaning,
relationships to other words, and opposites. You may want to search for words that are
near each other, or words that are related to thers. These queries would be extremely
difficult if all you had available was the standard relational operators. By extending SQL to
include text indexes, oracle text permits you to ask very complex questions about the
text.

To use oracle text, you need to create a text index on the column in which the text is
stored. Text index is a collection of tables and indexes that store information about the
text stored in the column.

TYPES


131

There are several different types of indexes available in oracle 9i. The first, CONTEXT is
supported in oracle 8i as well as oracle 9i. As of oracle 9i, you can use the CTXCAT text
index fo further enhance your text index management and query capabilities.

 CONTEXT

 CTXCAT

 CTXRULE

The CTXCAT index type supports the transactional synchronization of data between the
base table and its text index. With CONTEXT indexes, you need to manually tell oracle to
update the values in the text index after data changes in base table. CTXCAT index types do
not generate score values during the text queries.

HOW TO CREATE TEXT INDEX?

You can create a text index via a special version of the create index comman. For context
index, specify the ctxsys.context index type and for ctxcat index, specify the ctxsys.ctxcat
index type.

Ex:
Suppose you have a table called BOOKS with the following columns
Title, Author, Info.

SQL> create index book_index on books(info) indextype is ctxsys.context;
SQL> create index book_index on books(info) indextype is ctxsys.ctxcat;

TEXT QUERIES

Once a text index is created on the info column of BOOKS table, text-searching capabilities
increase dynamically.

CONTAINS & CATSEARCH

CONTAINS function takes two parameters – the column name and the search string.

Syntax:


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Contains(indexed_column, search_str);

If you create a CTXCAT index, use the CATSEARCH function in place of CONTAINS. CATSEARCH
takes three parameters – the column name, the search string and the index set.

Syntax:
Contains(indexed_column, search_str, index_set);

HOW A TEXT QEURY WORKS?

When a function such as CONTAINS or CATSEARCH is used in query, the text portion of the
query is processed by oracle text. The remainder of the query is processed just like a
regular query within the database. The result of the text query processing and the regular
query processing are merged to return a single set of records to the user.
SEARCHING FOR AN EXACT MATCH OF A WORD

The following queries will search for a word called ‘prperty’ whose score is greater than
zero.

SQL> select * from books where contains(info, ‘property’) > 0;
SQL> select * from books where catsearch(info, ‘property’, null) > 0;

Suppose if you want to know the score of the ‘property’ in each book, if score values for
individual searches range from 0 to 10 for each occurrence of the string within the text
then use the score function.

SQL> select title, score(10) from books where contains(info, ‘property’, 10) > 0;

SEARCHING FOR AN EXACT MATCH OF MULTIPLE WORDS

The following queries will search for two words.

SQL> select * from books where contains(info, ‘property AND harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property AND harvests’, null) > 0;

Instead of using AND you could hae used an ampersand(&). Before using this method, set
define off so the & character will not be seen as part of a variable name.


133

SQL> set define off
SQL> select * from books where contains(info, ‘property & harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property harvests’, null) > 0;

The following queries will search for more than two words.

SQL> select * from books where contains(info, ‘property AND harvests AND workers’) > 0;
SQL> select * from books where catsearch(info, ‘property harvests workers’, null) > 0;

The following queries will search for either of the two words.

SQL> select * from books where contains(info, ‘property OR harvests’) > 0;

Instead of OR you can use a vertical line (|).

SQL> select * from books where contains(info, ‘property | harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property | harvests’, null) > 0;

In the following queries the ACCUM(accumulate) operator adds together the scores of the
individual searches and compares the accumulated score to the threshold value.

SQL> select * from books where contains(info, ‘property ACCUM harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property ACCUM harvests’, null) > 0;

Instead of OR you can use a comma(,).

SQL> select * from books where contains(info, ‘property , harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property , harvests’, null) > 0;

In the following queries the MINUS operator subtracts the score of the second term’s
search from the score of the first term’s search.

SQL> select * from books where contains(info, ‘property MINUS harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property NOT harvests’, null) > 0;


134

Instead of MINUS you can use – and instead of NOT you can use ~.

SQL> select * from books where contains(info, ‘property - harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property ~ harvests’, null) > 0;

SEARCHING FOR AN EXACT MATCH OF A PHRASE

The following queries will search for the phrase. If the search phrase includes a reserved
word within oracle text, the you must use curly braces ({}) to enclose text.

SQL> select * from books where contains(info, ‘transactions {and} finances’) > 0;
SQL> select * from books where catsearch(info, ‘transactions {and} finances’, null) > 0;

You can enclose the entire phrase within curly braces, in which case any reserved words
within the phrase will be treated as part of the search criteria.

SQL> select * from books where contains(info, ‘{transactions and finances}’) > 0;
SQL> select * from books where catsearch(info, ‘{transactions and finances}’, null) > 0;

SEARCHING FOR WORDS THAT ARE NEAR EACH OTHER

The following queries will search for the words that are in between the search terms.

SQL> select * from books where contains(info, ‘workers NEAR harvests’) > 0;

Instead of NEAR you can use ;.

SQL> select * from books where contains(info, ‘workers ; harvests’) > 0;

In CONTEXT index queries, you can specify the maximum number of words between the
search terms.

SQL> select * from books where contains(info, ‘NEAR((workers, harvests),10)’ > 0;

USING WILDCARDS DURING SEARCHES


135

You can use wildcards to expand the list of valid search terms used during your query.
Just as in regular text-string wildcard processing, two wildcards are available.

% - percent sign; multiple-character wildcard
_ - underscore; single-character wildcard

SQL> select * from books where contains(info, ‘worker%’) > 0;
SQL> select * from books where contains(info, ‘work___’) > 0;

SEARCHING FOR WORDS THAT SHARE THE SAME STEM

Rather than using wildcards, you can use stem-expansion capabilities to expand the list
of text strings. Given the ‘stem’ of a word, oracle will expand the list of words to search
for to include all words having the same stem. Sample expansions are show here.
Play - plays playing played playful

SQL> select * from books where contains(info, ‘$manage’) > 0;

SEARCHING FOR FUZZY MATCHES

A fuzzy match expands the specified search term to include words that are spelled
similarly but that do not necessarily have the same word stem. Fuzzy matches are most
helpful when the text contains misspellings. The misspellings can be either in the
searched text or in the search string specified by the user during the query.

The following queries will not return anything because its search does not contain the
word ‘hardest’.

SQL> select * from books where contains(info, ‘hardest’) > 0;

It does, however, contains the word ‘harvest’. A fuzzy match will return the books
containing the word ‘harvest’ even though ‘harvest’ has a different word stem thant the
word used as the search term.

To use a fuzzy match, precede the search term with a question mark, with no space
between the question mark and the beginning of the search term.


136

SQL> select * from books where contains(info, ‘?hardest’) > 0;

SEARCHING FOR WORDS THAT SOUND LIKE OTHER WORDS

SOUNDEX, expands search terms based on how the word sounds. The SOUNDEX
expansion method uses the same text-matching logic available via the SOUNDEX function
in SQL.

To use the SOUNDEX option, you must precede the search term with an exclamation
mark(!).

SQL> select * from books where contains(info, ‘!grate’) > 0;

INDEX SYNCHRONIZATION

When using CONTEXT indexes, you need to manage the text index contents; the text
indexes are not updated when the base table is updated. When the table was updated, its
text index is out of sync with the base table. To sync of the index, execute the SYNC_INDEX
procedure of the CTX_DDL package.

SQL> exec CTX_DDL.SYNC_INDEX(‘book_index’);

INDEX SETS

Historically, problems with queries of text indexes have occurred when other criteria are
used alongside text searches as part of the where clause. To improve the mixed query
capability, oracle features index sets. The indexes within the index set may be structured
relational columns or on text columns.

To create an index set, use the CTX_DDL package to create the index set and add indexes to
it. When you create a text index, you can then specify the index set it belongs to.

SQL> exec CTX_DDL.CREATE_INDEX_SET(‘books_index_set’);

The add non-text indexes.


137

SQL> exec CTX_DDL.ADD_INDEX(‘books_index_set’, ‘title_index’);

Now create a CTXCAT text index. Specify ctxsys.ctxcat as the index type, and list the index
set in the parameters clause.

SQL> create index book_index on books(info) indextype is ctxsys.ctxcat
parameters(‘index set books_index_set’);

INDEX-ORGANIZED TABLE

An index-organized table keeps its data sorted according to the primary key column
values for the table. Index-organized tables store their data as if the entire table was
stored in an index.
An index-organized table allows you to store the entire table’s data in an index.
Ex:
SQL> create table student (sno number(2),sname varchar(10),smarks number(3)
constraint pk primary key(sno) organization index;

PARTITION INDEX

Similar to partitioning tables, oracle allows you to partition indexes too. Like table
partitions, index partitions could be in different tablespaces.

LOCAL INDEXES

 Local keyword tells oracle to create a separte index for each partition.
 In the local prefixed index the partition key is specified on the left prefix. When the
underlying table is partitioned baes on, say two columns then the index can be
prefixed on the first column specified.
 Local prefixed indexes can be unique or non unique.
 Local indexes may be easier to manage than global indexes.

Ex:
SQL> create index stud_index on student(sno) local;


138

GLOBAL INDEXES

 A global index may contain values from multiple partitions.
 An index is global prefixed if it is partitioned on the left prefix of the index columns.
 The global clause allows you to create a non-partitioned index.
 Global indexes may perform uniqueness checks faster than local (partitioned)
indexes.
 You cannot create global indexes for hash partitions or subpartitions.

Ex:
SQL> create index stud_index on student(sno) global;

Similar to table partitions, it is possible to move them from one device to another. But
unlike table partitions, movement of index partitions requires individual reconstruction of
the index or each partition (only in the case of global index).

Ex:
SQL> alter index stud_ind rebuild partition p2

 Index partitions cannot be dropped manually.
 They are dropped implicitly when the data they refer to is dropped from the
partitioned table.

MONITORING USE OF INDEXES

Once you turned on the monitoring the use of indexes, then we can check whether the
table is hitting the index or not.

To monitor the use of index use the follwing syntax.

Syntax:
alter index index_name monitoring usage;

then check for the details in V$OBJECT_USAGE view.


139

If you want to stop monitoring use the following.

Syntax:
alter index index_name nomonitoring usage;

DATA MODEL

 ALL_INDEXES
 DBA_INDEXES
 USER_INDEXES
 ALL_IND-COLUMNS
 DBA-IND_COLUMNS
 USER_IND_COLUMNS
 ALL_PART_INDEXES
 DBA_PART_INDEXES
 USER_PART_INDEXES
 V$OBJECT_USAGE


140

SQL*PLUS COMMNANDS

These commands does not require statement terminator and applicable to the sessions ,
those will be automatically cleared when session was closed.

BREAK

This will be used to breakup the data depending on the grouping.

Syntax:
Break or bre [on <column_name> on report]

COMPUTE

This will be used to perform group functions on the data.

Syntax:
Compute or comp [group_function of column_name on breaking_column_name or
report]

TTITLE


141

This will give the top title for your report. You can on or off the ttitle.

Syntax:
Ttitle or ttit [left | center | right] title_name skip n other_characters
Ttitle or ttit [on or off]

BTITLE

This will give the bottom title for your report. You can on or off the btitle.

Syntax:
Btitle or btit [left | center | right] title_name skip n other_characters
Btitle or btit [on or off]
Ex:
SQL> bre on deptno skip 1 on report
SQL> comp sum of sal on deptno
SQL> comp sum of sal on report
SQL> ttitle center 'EMPLOYEE DETAILS' skip1 center '----------------'
SQL> btitle center '** THANKQ **'
SQL> select * from emp order by deptno;

Output:

EMPLOYEE DETAILS
-----------------------

---------- ---------- --------- ------- -------------- -------- ---------- ----------
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000
7934 MILLER CLERK 7782 23-JAN-82 1300
---------- **********
8750 sum

7369 SMITH CLERK 7902 17-DEC-80 800 20


142

7876 ADAMS CLERK 7788 23-MAY-87 1100
7902 FORD ANALYST 7566 03-DEC-81 3000
7788 SCOTT ANALYST 7566 19-APR-87 3000
7566 JONES MANAGER 7839 02-APR-81 2975
---------- **********
10875 sum

7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400
7900 JAMES CLERK 7698 03-DEC-81 950
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0
7521 WARD SALESMAN 7698 22-FEB-81 1250 500
---------- **********
9400 sum
----------
sum 29025

** THANKQ **

CLEAR

This will clear the existing buffers or break or computations or columns formatting.

Syntax:
Clear or cle buffer | bre | comp | col;

Ex:
SQL> clear buffer
Buffer cleared
SQL> clear bre
Breaks cleared
SQL> clear comp
Computes cleared
SQL> clear col


143

Columns cleared

CHANGE

This will be used to replace any strings in SQL statements.

Syntax:
Change or c/old_string/new_string

If the old_string repeats many times then new_string replaces the first string only.

Ex:
SQL> select * from det;
select * from det
*
ERROR at line 1:
ORA-00942: table or view does not exist

SQL> c/det/dept
1* select * from dept
SQL> /

DEPTNO DNAME LOC
---------- ---------------- -----------
10 ACCOUNTING NEW YORK
20 RESEARCH ALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

COLUMN

This will be used to increase or decrease the width of the table columns.

Syntax:
Column or col <column_name> format <num_format|text_format>


144

Ex:
SQL> col deptno format 999
SQL> col dname format a10

SAVE

This will be used to save your current SQL statement as SQL Script file.

Syntax:
Save or sav <file_name>.[extension] replace or rep

If you want to save the filename with existing filename the you have to use replace
option.
By default it will take sql as the extension.

Ex:
SQL> save ss
Created file ss.sql
SQL> save ss replace
Wrote file ss.sql

EXECUTE

This will be used to execute stored subprograms or packaged subprograms.

Syntax:
Execute or exec <subprogram_name>

Ex:
SQL> exec sample_proc

SPOOL

This will record the data when you spool on, upto when you say spool off. By default it
will give lst as extension.


145

Syntax:
Spool on | off | out | <file_name>.[Extension]

Ex:
SQL> spool on

DEPTNO DNAME LOC
--------- -------------- ----------
20 RESEARCH DALLAS
30 SALES CHICAGO

SQL> spool off
SQL> ed on.lst


DEPTNO DNAME LOC
--------- -------------- ----------
20 RESEARCH DALLAS
30 SALES CHICAGO

SQL> spool off

LIST

This will give the current SQL statement.

Syntax:
List or li [start_line_number] [end_line_number]


146

Ex:
SQL> select
2 *
3 from
4 dept;
SQL> list
1 select
2 *
3 from
4* dept
SQL> list 1
1* select
SQL> list 3
3* from

SQL> list 1 3
1 select
2 *
3* from

INPUT

This will insert the new line to the current SQL statement.

Syntax:
Input or in <string>

Ex:
SQL> select *
SQL> list
1* select *
SQL> input from dept
SQL> list
1 select *
2* from dept


147

APPEND

This will adds a new string to the existing string in the SQL statement without any space.

Syntax:
Append or app <string>

Ex:
SQL> select *
SQL> list
1* select *
SQL> append from dept
SQL> list

DELETE

This will delete the current SQL statement lines.

Syntax:
Delete or del <start_line_number> [<end_line_number>]

Ex:
SQL> select
2 *
3 from
4 dept
5 where
6 deptno
7 >10;
SQL> list
1 select
2 *
3 from


148

4 dept
5 where
6 deptno
7* >10
SQL> del 1
SQL> list
1 *
2 from
3 dept
4 where
5 deptno
6* >10
SQL> del 2
SQL> list
1 *
2 dept
3 where
4 deptno
5* >10
SQL> del 2 4
SQL> list
1 *
2* >10
SQL> del
SQL> list
1 *

VARIABLE

This will be used to declare a variable.

Syntax:
Variable or var <variable_name> <variable_type>

Ex:


149

SQL> var dept_name varchar(15)
SQL> select dname into dept_name from dept where deptno = 10;

PRINT

This will be used to print the output of the variables that will be declared at SQL level.

Syntax:
Print <variable_name>

Ex:
SQL> print dept_name

DEPT_NAME
--------------
ACCOUNTING

START

This will be used to execute SQL scripts.

Syntax:
start <filename_name>.sql

Ex:
SQL> start ss.sql
SQL> @ss.sql -- this will execute sql script files only.

HOST

This will be used to interact with the OS level from SQL.

Syntax:
Host [operation]

Ex:


150

SQL> host
SQL> host dir

SHOW

Using this, you can see several commands that use the set command and status.

Syntax:
Show all | <set_command>

Ex:
SQL> show all
appinfo is OFF and set to "SQL*Plus"
arraysize 15
autocommit OFF
autoprint OFF
autorecovery OFF
autotrace OFF
blockterminator "." (hex 2e)
btitle OFF and is the first few characters of the next SELECT statement
cmdsep OFF
colsep " "
compatibility version NATIVE
concat "." (hex 2e)
copycommit 0
COPYTYPECHECK is ON
define "&" (hex 26)
describe DEPTH 1 LINENUM OFF INDENT ON
echo OFF
editfile "afiedt.buf"
embedded OFF
escape OFF
FEEDBACK ON for 6 or more rows
flagger OFF
flush ON


151

SQL> sho verify
verify OFF

RUN

This will runs the command in the buffer.

Syntax:
Run | /

Ex:
SQL> run
SQL> /
STORE

This will save all the set command statuses in a file.

Syntax:
Store set <filename>.[extension] [create] | [replace] | [append]

Ex:
SQL> store set my_settings.scmd
Created file my_settings.scmd
SQL> store set my_settings.cmd replace
Wrote file my_settings.cmd
SQL> store set my_settings.cmd append
Appended file to my_settings.cmd

FOLD_AFTER

This will fold the columns one after the other.

Syntax:
Column <column_name> fold_after [no_of_lines]

Ex:


152

SQL> col deptno fold_after 1
SQL> col dname fold_after 1
SQL> col loc fold_after 1
SQL> set heading off

10
ACCOUNTING
NEW YORK

20
RESEARCH
DALLAS
30
SALES
CHICAGO

40
OPERATIONS
BOSTON

FOLD_BEFORE

This will fold the columns one before the other.

Syntax:
Column <column_name> fold_before [no_of_lines]

DEFINE

This will give the list of all the variables currently defined.

Syntax:
Define [variable_name]

Ex:


153

SQL> define
DEFINE _DATE = "16-MAY-07" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oracle" (CHAR)
DEFINE _USER = "SCOTT" (CHAR)
DEFINE _PRIVILEGE = "" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1001000200" (CHAR)
DEFINE _EDITOR = "Notepad" (CHAR)
DEFINE _O_VERSION = "Oracle Database 10g Enterprise Edition Release
10.1.0.2.0 – Production With the Partitioning, OLAP and
Data Mining options" (CHAR)
DEFINE _O_RELEASE = "1001000200" (CHAR)

SET COMMANDS

These commands does not require statement terminator and applicable to the sessions ,
those will be automatically cleared when session was closed.

LINESIZE

This will be used to set the linesize. Default linesize is 80.

Syntax:
Set linesize <value>

Ex:
SQL> set linesize 100

PAGESIZE

This will be used to set the pagesize. Default pagesize is 14.

Syntax:
Set pagesize <value>

Ex:


154

SQL> set pagesize 30

DESCRIBE

This will be used to see the object’s structure.

Syntax:
Describe or desc <object_name>

Ex:
SQL> desc dept

Name Null? Type
----------------------------------------------------------------- ---------------------
DEPTNO NOT NULL NUMBER(2)
DNAME VARCHAR2(14)
LOC VARCHAR2(13)

PAUSE

When the displayed data contains hundreds or thousands of lines, when you select it then
it will automatically scrolls and displays the last page data. To prevent this you can use
this pause option. By using this it will display the data correspoinding to the pagesize
with a break which will continue by hitting the return key. By default this will be off.

Syntax:
Set pause on | off

Ex:
SQL> set pause on

FEEDBACK


155

This will give the information regarding howmany rows you selected the object. By
default the feedback message will be displayed, only when the object contains more than
5 rows.

Syntax:
Set feedback <value>

Ex:
SQL> set feedback 4

DEPTNO DNAME LOC
---------- -------------- -------------
20 RESEARCH DALLAS
30 SALES CHICAGO

4 rows selected.

HEADING

If you want to display data without headings, then you can achieve with this. By default
heading is on.

Syntax:
Set heading on | off

Ex:
SQL> set heading off

20 RESEARCH DALLAS
30 SALES CHICAGO


156


SERVEROUTPUT

This will be used to display the output of the PL/SQL programs. By default this will be off.

Syntax:
Set serveroutput on | off

Ex:
SQL> set serveroutput on

TIME

This will be used to display the time. By default this will be off.

Syntax:
Set time on | off

Ex:
SQL> set time on
19:56:33 SQL>

TIMING

This will give the time taken to execute the current SQL statement. By default this will be
off.

Syntax:
Set timing on | off

Ex:
SQL> set timing on


157


DEPTNO DNAME LOC
---------- -------------- -------------
20 RESEARCH DALLAS
30 SALES CHICAGO

Elapsed: 00:00:00.06

SQLPROMPT

This will be used to change the SQL prompt.
Syntax:
Set sqlprompt <prompt>

Ex:
SQL> set sqlprompt 'ORACLE>'
ORACLE>

SQLCASE

This will be used to change the case of the SQL statements. By default the case is mixed.

Syntax:
Set sqlcase upper | mixed | lower

Ex:
SQL> set sqlcase upper

SQLTERMINATOR

This will be used to change the terminator of the SQL statements. By default the
terminator is ;.


158

Syntax:
Set sqlterminator <termination_character>

Ex:
SQL> set sqlterminator :
SQL> select * from dept:

DEFINE

By default if the & character finds then it will treat as bind variable and ask for the input.
Suppose your want to treat it as a normal character while inserting data, then you can
prevent this by using the define option. By default this will be on

Syntax:
Set define on | off

Ex:
SQL>insert into dept values(50,'R&D','HYD');
Enter value for d:
old 1: insert into dept values(50,'R&D','HYD')
new 1: INSERT INTO DEPT VALUES(50,'R','HYD')

SQL> set define off
SQL>insert into dept values(50,'R&D','HYD'); -- here it won’t ask for value

NEWPAGE

This will shows how many blank lines will be left before the report. By default it will leave
one blank line.

Syntax:
Set newpage <value>

Ex:


159

SQL> set newpage 10

The zero value for newpage does not produce zero blank lines instead it switches to a
special property which produces a top-of-form character (hex 13) just before the date on
each page. Most modern printers respond to this by moving immediately to the top of the
next page, where the priting of the report will begin.

HEADSEP

This allow you to indicate where you want to break a page title or a column heading that
runs longer than one line. The default heading separator is vertical bar (|).

Syntax:
Set headsep <separation_char>
Ex:

DEPTNO DNAME LOC
---------- -------------- -------------
20 RESEARCH DALLAS
30 SALES CHICAGO

SQL> set headsetp !
SQL> col dname heading 'DEPARTMENT ! NAME'
SQL> /

DEPARTMENT
DEPTNO NAME LOC
---------- ----------------- ----------
20 RESEARCH DALLAS
30 SALES CHICAGO


160

ECHO

When using a bind variable, the SQL statement is maintained by echo. By default this is
off.

Syntax:
Set echo on | off

VERIFY

When using a bind variable, the old and new statements will be maintained by verify. By
default this is on.

Syntax:
Set verify on | off

Ex:
SQL> select * from dept where deptno = &dno;
Enter value for dno: 10
old 1: select * from dept where deptno = &dno
new 1: select * from dept where deptno = 10

DEPTNO DNAME LOC
---------- ---------------- -----------

SQL> set verify off
SQL> select * from dept where deptno = &dno;
Enter value for dno: 20

DEPTNO DNAME LOC
---------- ------------- -----------
20 RESEARCH DALLAS


161

PNO

This will give displays the page numbers. By default the value would be zero.

Ex:
SQL> col hiredate new_value xtoday noprint format a1 trunc
SQL> ttitle left xtoday right 'page' sql.pno
SQL> select * from emp where deptno = 10;

09-JUN-81 page 1

EMPNO ENAME JOB MGR SAL COMM DEPTNO
---------- ---------- --------------- --------- ----- ---------- ----------
7782 CLARK MANAGER 7839 2450 10
7839 KING PRESIDENT 5000 10
7934 MILLER CLERK 7782 1300 10

In the above noprint tells SQLPLUS not to display this column when it prints the results of
the SQL statement. Dates that have been reformatted by TO_CHAR get a default width of
about 100 characters. By changing the format to a1 trunc, you minimize this effect.
NEW_VALUE inserts contents of the column retrieved by the SQL statement into a variable
called xtoday.


162

SPECIAL FILES

LOGIN.sql

If you would like SQLPLUS to define your own environmental settings, put all the required
commands in a file named login.sql. This is a special filename that SQLPLUS always looks
for whenever it starts up. If it finds login.sql, it executes any commands in it as if you had
entered then by hand. You can put any command in login.sql that you can use in SQLPLUS,
including SQLPLUS commands and SQL statements. All ot them executed before SQLPLUS
gives you the SQL> prompt.

GLOGIN.sql

This is used in the same ways as LOGIN.sql but to establish default SQLPLUS settings for all
users of a database.


163

IMPORTANT QUERIES

1) To find the nth row of a table

SQL> Select *from emp where rowid = (select max(rowid) from emp where rownum
<= 4);
Or
SQL> Select *from emp where rownum <= 4 minus select *from emp where rownum
<= 3;

2) To find duplicate rows

SQL> Select *from emp where rowid in (select max(rowid) from emp group by
empno, ename, mgr, job, hiredate, comm, deptno, sal);
Or
SQL> Select empno,ename,sal,job,hiredate,comm , count(*) from emp group by
empno,ename,sal,job,hiredate,comm having count(*) >=1;

3) To delete duplicate rows

SQL> Delete emp where rowid in (select max(rowid) from emp group by


164

empno,ename,mgr,job,hiredate,sal,comm,deptno);

4) To find the count of duplicate rows

SQL> Select ename, count(*) from emp group by ename having count(*) >= 1;

5) How to display alternative rows in a table?

SQL> select *from emp where (rowid,0) in (select rowid,mod(rownum,2) from emp);

6) Getting employee details of each department who is drawing maximum sal?

SQL> select *from emp where (deptno,sal) in
( select deptno,max(sal) from emp group by deptno);
7) How to get number of employees in each department , in which department is
having more than 2500 employees?

SQL> Select deptno,count(*) from emp group by deptno having count(*) >2500;

8) To reset the time to the beginning of the day

SQL> Select to_char(trunc(sysdate),’dd-mon-yyyy hh:mi:ss am’) from dual;

9) To find nth maximum sal

SQL> Select *from emp where sal in (select max(sal) from (select *from emp order
by sal) where rownum <= 5);


165

INTRODUCTION

CHARACTERSTICS

 Highly structured, readable and accessible language.
 Standard and Protable language.
 Embedded language.
 Improved execution authority.

10g FEATURES

 Optimized compiler
.
To change the optimizer settings for the entire database, set the database
parameter PLSQL_OPTIMIZE_LEVEL. Valid settings are as follows
0 - No optimization
1 - Moderate optimization
2 - Aggressive optimization

These settings are also modifiable for the current session.
SQL> alter session set plsql_optimze_level=2;


166

Oracle retains optimizer settings on a module-by-module basis. When you
recompile a particular module with nondefault settings, the settings will stick
allowing you to recompile later on using REUSE SETTINGS.

SQL> Alter procedure proc compile plsql_optimize_level=1;
SQL> Alter procedure proc compile reuse settings;

 Compile-time warnings.

Starting with oracle database 10g release 1 you can enable additional compile-time
warnings to help make your programs more robust. The compiler can detect
potential runtime problems with your code, such as identifying lines of code that
will never be run. This process, also known as lint checking.
To enable these warnings fo the entire database, set the database parameter
PLSQL_WARNINGS. These settings are also modifiable for the current session.

SQL> alter session set plsql_warnings = ‘enable:all’;
The above can be achieved using the built-in package DBMS_WARNING.

 Conditional compilation.

Conditional compilation allows the compiler to allow to compile selected parts of a
program based on conditions you provide with the $IF directive.

 Support for non-sequential collections in FORALL.
 Improved datatype support.

 Backtrace an exception to its line number.

When handling an error, how can you find the line number on which the error was
originally raised?

In earlier release, the only way to do this was allow you exception to go unhandled
and then view the full error trace stack.


167

Now you can call DBMS_UTILITY.FORMAT_ERROR_BACKTRACE function to obtain that stack
and manipulate it programmatically within your program.

 Set operators for nested tables.

 Support for regular expressions.

Oracle database 10g supports the use of regular expressions inside PL/SQL code via
four new built-in functions.

 REGEXP_LIKE
 REGEXP_INSTR
 REGEXP_SUBSTR
 REGEXP_REPLACE

 Programmer-defined quoting mechanism.

Starting with oracle database 10g release 1, you can define your own quoting
mechanism for string literals in both SQL and PL/SQL.

Use the characters q’(q followed by a single quote) to note the programmer-
defined deliemeter for you string literal.

Ex:
DECLARE

v varchar(10) := 'computer';
BEGIN

dbms_output.put_line(q'*v = *' || v);
dbms_output.put_line(q'$v = $' || v);
END;

Output:
v = computer
v = computer

 Many new built-in packages.


168

DBMS_SCHEDULER
Represents a major update to DBMS_JOB. DBMS_SCHEDULER provides much improved
functionality for scheduling and executing jobs defined via stored procedures.

DBMS_CRYPTO
Offers the ability to encrypt and decrypt common oracle datatype, including RAWs,
BLOBs, and CLOBs. It also provides globalization support for encrypting data across
different charactersets.

DBMS_MONITOR
Provides an API to control additional tracing and statistics gathering of sessions.

DBMS_WARNING
Provides an API into the PL/SQL compiler warnings module, allowing you to read and
change settings that control which warnings are suppressed, displayed, or treated
as errors.

STANDARD PACKAGE

Oracle has defined in this special package. Oracle defines quite a few identifiers in this
package, including built-in exceptions, functions and subtypes.
You can reference the built-in form by prefixing it with STANDARD.

The basic unit in any PL/SQL program is block. All PL/SQL programs are composed of blocks
which can occur sequentially or nested.

BLOCK STRUCTURE

Declare
-- declarative section
Begin
-- executable section
Exception


169

-- exception section
End;

In the above declarative and exceptiona sections are optional.

BLOCK TYPES

 Anonymous blocks
 Named blocks
 Labeled blocks
 Subprograms
 Triggers

ANONYMOUS BLOCKS

Anonymous blocks implies basic block structure.

Ex:
BEGIN

Dbms_output.put_line(‘My first program’):
END;

LABELED BLOCKS

Labeled blocks are anonymous blocks with a label which gives a name to the block.

Ex:
<<my_bloock>>
BEGIN

Dbms_output.put_line(‘My first program’):
END;

SUBPROGRAMS


170

Subprograms are procedures and functions. They can be stored in the database as stand-
alone objects, as part of package or as methods of an object type.

TRIGGERS

Triggers consists of a PL/SQL block that is associated with an event that occur in the
database.

NESTED BLOCKS

A block can be nested within the executable or exception section of an outer block.

IDENTIFIERS

Identifiers are used to name PL/SQL objects, such as variables, cursors, types and
subprograms. Identifiers consists of a letter, optionally followed by any sequence of
characters, including letters, numbers, dollar signs, underscores, and pound signs only.
The maximum length for an identifier is 30 characters.

QUOTED IDENTIFIERS

If you want to make an identifier case sensitive, include characters such as spaces or use
a reserved word, you can enclose the identifier in double quotation marks.

Ex:
DECLARE

"a" number := 5;
"A" number := 6;
BEGIN

dbms_output.put_line('a = ' || a);
dbms_output.put_line('A = ' || A);
END;

Output:
a=6
A=6


171

COMMENTS

Comments improve readability and make your program more understandable. They are
ignored by the PL/SQL compiler. There are two types of comments available.

 Single line comments
 Multiline comments

SINGLE LINE COMMENTS

A single-line comment can start any point on a line with two dashes and continues until
the end of the line.

Ex:
BEGIN

Dbms_output.put_line(‘hello’); -- sample program
END;
MULTILINE COMMENTS

Multiline comments start with the /* delimiter and ends with */ delimiter.

Ex:
BEGIN

Dbms_output.put_line(‘hello’); /* sample program */
END;

VARIABLE DECLERATIONS

Variables can be declared in declarative section of the block;

Ex:
DECLARE

a number;
b number := 5;
c number default 6;

CONSTANT DECLERATIONS


172

To declare a constant, you include the CONSTANT keyword, and you must supply a default
value.

Ex:
DECLARE

b constant number := 5;
c constant number default 6;

NOT NULL CLAUSE

You can also specify that the variable must be not null.

Ex:
DECLARE

b constant number not null:= 5;
c number not null default 6;
ANCHORED DECLERATIONS

PL/SQL offers two kinds of achoring.
 Scalar anchoring
 Record anchoring

SCALAR ANCHORING

Use the %TYPE attribute to define your variable based on table’s column of some other
PL/SQL scalar variable.

Ex:
DECLARE

dno dept.deptno%type;
Subtype t_number is number;
a t_number;
Subtype t_sno is student.sno%type;
V_sno t_sno;

RECORD ANCHORING


173

Use the %ROWTYPE attribute to define your record structure based on a table.

Ex:
`DECLARE
V_dept dept%rowtype;

BENEFITS OF ANCHORED DECLARATIONS

 Synchronization with database columns.
 Normalization of local variables.

PROGRAMMER-DEFINED TYPES

With the SUBTYPE statement, PL/SQL allows you to define your own subtypes or aliases of
predefined datatypes, sometimes referred to as abstract datatypes.
There are two kinds of subtypes.
 Constrained
 Unconstrained

CONSTRAINED SUBTYPE

A subtype that restricts or constrains the values normally allowd by the datatype itself.

Ex:
Subtype positive is binary_integer range 1..2147483647;

In the above declaration a variable that is declared as positive can store only ingeger
greater than zero even though binary_integer ranges from -2147483647..+2147483647.

UNCONSTRAINED SUBTYPE

A subtype that does not restrict the values of the original datatype in variables declared
with the subtype.

Ex:


174

Subtype float is number;

DATATYPE CONVERSIONS

PL/SQL can handle conversions between different families among the datatypes.
Conversion can be done in two ways.

 Explicit conversion
 Implicit conversion

EXPLICIT CONVERSION

This can be done using the built-in functions available.

IMPLICIT CONVERSION

PL/SQL will automatically convert between datatype families when possible.
Ex:
DECLARE

a varchar(10);
BEGIN

select deptno into a from dept where dname='ACCOUNTING';
END;

In the above variable a is char type and deptno is number type even though, oracle will
automatically converts the numeric data into char type assigns to the variable.
PL/SQL can automatically convert between

 Characters and numbers
 Characters and dates

VARIABLE SCOPE AND VISIBILITY

The scope of a variable is the portion of the program in which the variable can be
accessed. For PL/SQL variables, this is from the variable declaration until the end of the


175

block. When a variable goes out of scope, the PL/SQL engine will free the memory used to
store the variable.

The visibility of a variable is the portion of the program where the variable can be
accessed without having to qualify the reference. The visibility is always within the scope.
If it is out of scope, it is not visible.

Ex1:
DECLARE

a number; -- scope of a
BEGIN
--------
DECLARE

b number; -- scope of b
BEGIN

-----
END;

------
END;

Ex2:
DECLARE

a number;
b number;
BEGIN

-- a , b available here
DECLARE

b char(10);
BEGIN

-- a and char type b is available here
END;

-----
END;

Ex3:
<<my_block>>
DECLARE

a number;
b number;


176

BEGIN

-- a , b available here
DECLARE

b char(10);
BEGIN

-- a and char type b is available here
-- number type b is available using <<my_block>>.b
END;

------
END;

PL/SQL CONTROL STRUCTURES

PL/SQL has a variety of control structures that allow you to control the behaviour of the
block as it runs. These structures include conditional statements and loops.

 If-then-else
 Case
 Case with no else
 Labeled case
 Searched case
 Simple loop
 While loop
 For loop
 Goto and Labels

IF-THEN-ELSE

Syntax:
If <condition1> then
Sequence of statements;
Elsif <condition1> then
……
Else


177

End if;

Ex:
DECLARE

dno number(2);
BEGIN

select deptno into dno from dept where dname = 'ACCOUNTING';
if dno = 10 then
dbms_output.put_line('Location is NEW YORK');
elsif dno = 20 then
dbms_output.put_line('Location is DALLAS');
elsif dno = 30 then
dbms_output.put_line('Location is CHICAGO');
else
dbms_output.put_line('Location is BOSTON');
end if;
END;

Output:
Location is NEW YORK

CASE

Syntax:
Case test-variable
When value1 then sequence of statements;
……
When valuen then sequence of statements;
Else sequence of statements;
End case;

Ex:
DECLARE

dno number(2);


178

BEGIN

case dno
when 10 then
when 20 then
when 30 then
else
end case;
END;

Output:

CASE WITHOUT ELSE

Syntax:
Case test-variable
……
End case;

Ex:
DECLARE

dno number(2);
BEGIN

case dno
when 10 then


179

when 20 then
when 30 then
when 40 then
end case;
END;

Output:

LABELED CASE

Syntax:
<<label>>
Case test-variable
……
End case;

Ex:
DECLARE

dno number(2);
BEGIN

<<my_case>>
case dno
when 10 then
when 20 then
when 30 then


180

when 40 then
end case my_case;
END;

Output:

SEARCHED CASE

Syntax:
Case
When <condition1> then sequence of statements;
When <condition2> then sequence of statements;
……
When <conditionn> then sequence of statements;
End case;

Ex:
DECLARE

dno number(2);
BEGIN

case dno
when dno = 10 then
when dno = 20 then
when dno = 30 then
when dno = 40 then
end case;
END;


181

Output:

SIMPLE LOOP

Syntax:
Loop
Exit when <condition>;
End loop;

In the syntax exit when <condition> is equivalent to
If <condition> then
Exit;
End if;

Ex:
DECLARE

i number := 1;
BEGIN

loop
dbms_output.put_line('i = ' || i);
i := i + 1;
exit when i > 5;
end loop;
END;

Output:
i=1
i=2
i=3
i=4
i=5

WHILE LOOP


182

Syntax:
While <condition> loop
End loop;

Ex:
DECLARE

i number := 1;
BEGIN

While i <= 5 loop
i := i + 1;
end loop;
END;

Output:
i=1
i=2
i=3
i=4
i=5

FOR LOOP

Syntax:
For <loop_counter_variable> in low_bound..high_bound loop
End loop;

Ex1:
BEGIN

For i in 1..5 loop
end loop;
END;

Output:


183

i=1
i=2
i=3
i=4
i=5

Ex2:
BEGIN

For i in reverse 1..5 loop
end loop;
END;

Output:
i=5
i=4
i=3
i=2
i=1

NULL STATEMENT

Usually when you write a statement in a program, you want it to do something. There are
cases, however, when you want to tell PL/SQL to do absolutely nothing, and that is where
the NULL comes.

The NULL statement deos nothing except pass control to the next executable statement.
You can use NULL statement in the following situations.

 Improving program readability.
Sometimes, it is helpful to avoid any ambiguity inherent in an IF statement that
doesn’t cover all possible cases. For example, when you write an IF statement, you do
not have to include an ELSE clause.

 Nullifying a raised exception.


184

When you don’t want to write any special code to handle an exception, you can use the
NULL statement to make sure that a raised exception halts execution of the current
PL/SQL block but does not propagate any exceptions to enclosing blocks.

 Using null after a label.
In some cases, you can pair NULL with GOTO to avoid having to execute additional
statements. For example, I use a GOTO statement to quickly move to the end of my
program if the state of my data indicates that no further processing is required.
Because I do not have to do anything at the termination of the program, I place a NULL
statement after the label because at least one executable statement is required there.
Even though NULL deos nothing, it is still an executable statement.

GOTO AND LABELS

Syntax:
Goto label;

Where label is a label defined in the PL/SQL block. Labels are enclosed in double angle
brackets. When a goto statement is evaluated, control immediately passes to the
statement identified by the label.
Ex:
BEGIN

For i in 1..5 loop
if i = 4 then
goto exit_loop;
end if;
end loop;
<<exit_loop>>
Null;
END;

Output:
i=1
i=2
i=3


185

i=4

RESTRICTIONS ON GOTO

 It is illegal to branch into an inner block, loop.
 At least one executable statement must follow.

 It is illegal to branch into an if statement.
 It is illegal to branch from one if statement to another if statement.
 It is illegal to branch from exception block to the current block.

PRAGMAS

Pragmas are compiler directives. They serve as instructions to the PL/SQL compiler. The
compiler will act on the pragma during the compilation of the block.

Syntax:
PRGAMA instruction_to_compiler.

PL/SQL offers several pragmas:

 AUTONOMOUS_TRANSACTION
 EXCEPTION_INIT
 RESTRICT_REFERENCES

 SERIALLY_REUSABLE


186

SUBPROGRAMS

PROCEDURES

A procedure is a module that performs one or more actions.

Syntax:
Procedure [schema.]name [(parameter1 [,parameter2 …])]
[authid definer | current_user] is
-- [declarations]
Begin
-- executable statements
[Exception
-- exception handlers]


187

End [name];

In the above authid clause defines whether the procedure will execute under the
authority of the definer of the procedure or under the authority of the current user.

FUNCTIONS

A function is a module that returns a value.

Syntax:
Function [schema.]name [(parameter1 [,parameter2 …])]
Return return_datatype
[authid definer | current_user]
[deterministic]
[parallel_enable] is
-- [declarations]
Begin
-- executable statements
[Exception
-- exception handlers]
End [name];
In the above authid clause defines whether the procedure will execute under the
authority of the definer of the procedure or under the authority of the current user.

Deterministic clause defines, an optimization hint that lets the system use a saved copy of
the function’s return result, if available. The quety optimizer can choose whether to use
the saved copy or re-call the function.

Parallel_enable clause defines, an optimization hint that enables the function to be
executed in parallel when called from within SELECT statement.

PARAMETER MODES

 In (Default)
 Out


188

 In out

IN

In parameter will act as pl/sql constant.

OUT

 Out parameter will act as unintialized variable.
 You cannot provide a default value to an out parameter.
 Any assignments made to out parameter are rolled back when an exception is
raised in the program.

 An actual parameter corresponding to an out formal parameter must be a variable.

IN OUT

 In out parameter will act as initialized variable.
 An actual parameter corresponding to an in out formal parameter must be a
variable.

DEFAULT PARAMETERS

Default Parameters will not allow in the beginning and middle.
Out and In Out parameters can not have default values.

Ex:
procedure p(a in number default 5, b in number default 6, c in number default 7) –
valid
procedure p(a in number, b in number default 6, c in number default 7) – valild
procedure p(a in number, b in number, c in number default 7) – valild
procedure p(a in number, b in number default 6, c in number) – invalild
procedure p(a in number default 5, b in number default 6, c in number) – invalild
procedure p(a in number default 5, b in number, c in number) – invalild


189

NOTATIONS

Notations are of two types.

 Positional notation
 Name notation

We can combine positional and name notation but positional notation can not be followed
by the name notation.

Ex:
Suppose we have a procedure proc(a number,b number,c number) and we have one
anonymous block which contains v1,v2, and v3;

SQL> exec proc (v1,v2,v3) -- Positional notation
SQL> exec proc (a=>v1,b=>v2,c=>v3) -- Named notation

FORMAL AND ACTUAL PARAMETERS

 Parametes which are in calling subprogram are actual parameters.
 Parametes which are in called subprogram are formal parameters.
 If any subprogram was called, once the call was completed then the values of
formal
parameters are copied to the actual parameters.

Ex1:
CREATE OR REPLACE PROCEDURE SAMPLE(a in number,b out number,c in out
number) is
BEGIN

dbms_output.put_line('After call');
dbms_output.put_line('a = ' || a ||' b = ' || b || ' c = ' || c);
b := 10;
c := 20;
dbms_output.put_line('After assignment');


190

dbms_output.put_line('a = ' || a ||' b = ' || b || ' c = ' || c);
END SAMPLE;

DECLARE

v1 number := 4;
v2 number := 5;
v3 number := 6;
BEGIN

dbms_output.put_line('Before call');
dbms_output.put_line('v1 = ' || v1 || ' v2 = ' || v2 || ' v3 = ' || v3);
sample(v1,v2,v3);
dbms_output.put_line('After completion of call');
END;

Output:
Before call
v1 = 4 v2 = 5 v3 = 6
After call
a=4b= c=6
After assignment
a = 4 b = 10 c = 20
After completion of call
v1 = 4 v2 = 10 v3 = 20
Ex2:
CREATE OR REPLACE FUN(a in number,b out number,c in out number) return
number IS
BEGIN

dbms_output.put_line('After call');
dbms_output.put_line('a = ' || a || ' b = ' || b || ' c = ' || c);
dbms_output.put_line('Before assignement Result = ' || (a*nvl(b,1)*c));
b := 5;
c := 7;
dbms_output.put_line('After assignment');
dbms_output.put_line('a = ' || a || ' b = ' || b || ' c = ' || c);
return (a*b*c);
END FUN;


191

DECLARE

v1 number := 1;
v2 number := 2;
v3 number := 3;
v number;
BEGIN

dbms_output.put_line('Before call');
v := fun(v1,v2,v3);
dbms_output.put_line('After call completed');
dbms_output.put_line('Result = ' || v);
END;

Output:
Before call
v1 = 1 v2 = 2 v3 = 3
After call
a=1b= c=3
Before assignement Result = 3
After assignment
a=1b=5c=7
After call completed
v1 = 1 v2 = 5 v3 = 7
Result = 35

RESTRICTIONS ON FORMAL PARAMETERS

 By declaring with specified size in actual parameters.
 By declaring formal parameters with %type specifier.

USING NOCOPY

 Nocopy is a hint, not a command. This means that the compiler might silently
decide that it can’t fulfill your request for a nocopy parameter.


192

 The copying from formal to actual can be restricted by issuing nocopy qualifier.
 To pass the out and in out parameters by reference use nocopy qualifier.

Ex:
CREATE OR REPLACE PROCEDURE PROC(a in out nocopy number) IS
BEGIN
----
END PROC;

CALL AND EXEC

Call is a SQL statement, which can be used to execute subprograms like exec.

Syntax:
Call subprogram_name([argument_list]) [into host_variable];

 The parantheses are always required, even if the subprogram takes no arguments.

 We can not use call with out and in out parameters.
 Call is a SQL statement, it is not valid inside a PL/SQL block;
 The INTO clause is used for the output variables of functions only.
 We can not use ‘exec’ with out or in out parameters.
 Exec is not valid inside a PL/SQL block;

Ex1:
CREATE OR REPLACE PROC IS
BEGIN

dbms_output.put_line('hello world');
END PROC;

Output:
SQL> call proc();
hello world

Ex2:


193

CREATE OR REPLACE PROC(a in number,b in number) IS
BEGIN

dbms_output.put_line('a = ' || a || ' b = ' || b);
END PROC;

Output:
SQL> call proc(5,6);
a=5b=6

Ex3:
CREATE OR REPLACE FUNCTION FUN RETURN VARCHAR IS
BEGIN

return 'hello world';
END FUN;

Output:
SQL> variable v varchar(20)
SQL> call fun() into :v;
SQL> print v
hello world

CALL BY REFERENCE AND CALL BY VALUE

 In parameters by default call by reference where as out and in out call by value.
 When parameter passed by reference, a pointer to the actual parameter is passed
to the corresponding formal parameter.

 When parameter passed by value it copies the value of the actual parameter to the
formal parameter.
 Call by reference is faster than the call by value because it avoids the copying.

SUBPROGRAMS OVERLOADING

 Possible with different number of parameters.
 Possible with different types of data.
 Possible with same type with objects.


194

 Can not be possible with different types of modes.
 We can overload local subprograms also.

Ex:
SQL> create or replace type t1 as object(a number);/
SQL> create or replace type t1 as object(a number);/

DECLARE

i t1 := t1(5);
j t2 := t2(5);
PROCEDURE P(m t1) IS
BEGIN

dbms_output.put_line('a = ' || m.a);
END P;
PROCEDURE P(n t2) IS
BEGIN

dbms_output.put_line('b = ' || n.b);
END P;
PROCEDURE PRODUCT(a number,b number) IS
BEGIN

dbms_output.put_line('Product of a,b = ' || a * b);
END PRODUCT;
PROCEDURE PRODUCT(a number,b number,c number) IS
BEGIN

dbms_output.put_line('Product of a,b = ' || a * b * c);
END PRODUCT;
BEGIN

p(i);
p(j);
product(4,5);
product(4,5,6);
END;

Output:
a=5
b=5
Product of a,b = 20
Product of a,b = 120


195

BENEFITS OF OVERLOADING

 Supporting many data combinations
 Fitting the program to the user.

RESTRICTIONS ON OVERLOADING

 Overloaded programs with parameter lists that differ only by name must be called
using named notation.
 The parameter list of overloaded programs must differ by more than parameter
mode.

 All of the overloaded programs must be defined within the same PL/SQL scope or
block.
 Overloaded functions must differ by more than their return type.

IMPORTANT POINTS ABOUT SUBPROGRAMS

 When a stored subprogram is created, it is stored in the data dictionary.
 The subprogram is stored in compile form which is known as p-code in addition to
the source text.

 The p-code has all of the references in the subprogram evaluated, and the source
code is translated into a form that is easily readable by PL/SQL engine.
 When the subprogram is called, the p-code is read from the disk, if necessary, and
executed.

 Once it reads from the disk, the p-code is stored in the shared pool portion of the
system global area (SGA), where it can be accessed by multiple users as needed.

 Like all of the contents of the shared pool, p-code is aged out of the shared pool
according to a least recently used (LRU) algorithm.

 Subprograms can be local.
 Local subprograms must be declared in the declarative section of PL/SQL block and
called from the executable section.
 Subprograms can not have the declarative section separately.
 Stored subprograms can have local subprograms;


196

 Local subprograms also can have local subprograms.

 If the subprogram contains a variable with the same name as the column name of
the table then use the dot method to differentiate (subprogram_name.sal).
 Subprograms can be invalidated.

PROCEDURES V FUNCTIONS

 Procedures may return through out and in out parameters where as function must
return.
 Procedures can not have return clause where as functions must.
 We can use call statement directly for executing procedure where as we need to
declare a variable in case of functions.
 Functions can use in select statements where as procedures can not.
 Functions can call from reports environment where as procedures can not.
 We can use exec for executing procedures where as functions can not.
 Function can be used in dbms_output where as procedure can not.
 Procedure call is a standalone executable statement where as function call is a part
of an executable statement.

STORED V LOCAL SUBPROGRAMS

 The stored subprogram is stored in compiled p-code in the database, when the
procedure is called it does not have to be compiled.
The local subprogram is compiled as part of its containing block. If the containing
block is anonymous and is run multiple times, the subprogram has to be compiled
each time.

 Stored subprograms can be called from any block submitted by a user who has
execute privileges on the subprogram.
Local subprograms can be called only from the block containing the subprogram.
 By keeping the stored subprogram code separate from the calling block, the calling
block is shorter and easier to understand.
The local subprogram and the calling block are one and the same, which can lead to
part confusion. If a change to the calling block is made, the subprogram will be
recompiled as of the recompilation of the containing block.


197

 The compiled p-code can be pinned in the shared pool using the
DBMS_SHARED_POOL Package. This can improve performance.
Local subprograms cannot be pinned in the shared pool by themselves.

 Stand alone stored subprograms can not be overloaded, but packaged subprograms
can be overloaded within the same package.
 Local subprograms can be overloaded within the same block.

Ex1:
CREATE OR REPLACE PROCEDURE P IS
BEGIN

dbms_output.put_line('Stored subprogram');
END;

Output:
SQL> exec p
Stored subprogram

Ex2:
DECLARE
PROCEDURE P IS
BEGIN

dbms_output.put_line('Local subprogram');
END;
BEGIN

p;
END;

Output:
Local subprogram
COMPILING SUBPROGRAMS

 SQL> Alter procedure P1 compile;

 SQL> Alter function F1 compile;

SUBPROGRAMS DEPENDECIES


198

 A stored subprogram is marked as invalid in the data dictionary if it has compile
errors.
 A stored subprogram can also become invalid if a DDL operation is performed on
one of its dependent objects.

 If a subprogram is invalidated, the PL/SQL engine will automatically attempt to
recompile in the next time it is called.

 If we have two procedures like P1 and P2 in which P1 depends on P2. If we compile
P2 then P1 is invalidated.

SUBPROGRAMS DEPENDENCIES IN REMOTE DATABASES

 We will call remote subprogram using connect string like P1@ORACLE;
 If we have two procedures like P1 and P2 in which P1 depends on P2 but P2 was in
remote database. If we compile P2 it will not invalidate P1 immediately because
the data dictionary does not track remote dependencies.

 Instead the validity of remote objects is checked at runtime. When P1 is called, the
remote data dictionary is queried to determine the status of P2.
 P1 and P2 are compared to see it P1 needs to be recompiled, there are two
different methods of comparision
 Timestamp Model
 Signature Model

TIMESTAMP MODEL

 This is the default model used by oracle.
 With this model, the timestamps of the last modifications of the two objects are
compared.

 The last_ddl_time field of user_objects contains the timestamp.
 If the base object has a newer timestamp than the dependent object, the
dependent object will be recompiled.

ISSUES WITH THIS MODEL

 If the objects are in different time zones, the comparison is invalid.


199

 When P1 is in a client side PL/SQL engine such as oracle forms, in this case it may
not possible to recompile P1, because the source for it may not be included with
the forms.

SIGNATURE MODEL

 When a procedure is created, a signature is stored in the data dictionary in addition
to the p-code.
 The signature encodes the types and order of the parametes.
 When P1 is compiled the first time, the signature of P2 is included. Thus, P1 only
needs to recompiled when the signature of P2 changes.

 In order to use the signature model, the parameter REMOTE_DEPENDENCIES_MODE must
be set to SIGNATURE. This is a parameter in the database initialization file.

THREE WAYS OF SETTING THIS MODE

 Add the line REMOTE_DEPENDENCIES_MODE=SIGNATURE to the database initialization file.
The next time the database is started, the mode will be set to SIGNATURE for all
sessions.
 Alter system set remote_dependencies_mode = signature;
This will affect the entire database (all sessions) from the time the statement is
issued. You must have the ALTER SYSTEM privilege to issue this command.
 Alter session set remote_dependencies_mode = signature;
This will only affect your session

ISSUES WITH THIS MODEL

 Signatures don’t get modified if the default values of formal parameters are
changed.

 Suppose P2 has a default value for one of its parameters, and P1 is using this
default value. If the default in the specification for P2 is changed, P1 will not be
recompiled by default. The old value for the default parameter will still be used until
P1 is manually recompiled.


200

 If P1 is calling a packaged procedure P2, and a new overloaded version of P2 is
added to the remote package, the signature is not changed. P1 will still use the old
version(not the new overloaded one) until P1 is recompiled manually.

FORWARD DECLERATION

Before going to use the procedure in any other subprogram or other block , you must
declare the prototype of the procedure in declarative section.

Ex1:
DECLARE
PROCEDURE P1 IS
BEGIN

dbms_output.put_line('From procedure p1');
p2;
END P1;
PROCEDURE P2 IS
BEGIN

p3;
END P2;
PROCEDURE P3 IS
BEGIN

END P3;
BEGIN

p1;
END;

Output:
p2;
*
ERROR at line 5:
ORA-06550: line 5, column 1:
PLS-00313: 'P2' not declared in this scope
PL/SQL: Statement ignored


201

PLS-00313: 'P3' not declared in this scope
PL/SQL: Statement ignored

Ex2:
DECLARE

PROCEDURE P2; -- forward declaration
PROCEDURE P3;
PROCEDURE P1 IS
BEGIN

p2;
END P1;
PROCEDURE P2 IS
BEGIN

p3;
END P2;
PROCEDURE P3 IS
BEGIN

END P3;
BEGIN

p1;
END;

Output:
From procedure p1
From procedure p2
From procedure p3

PRIVILEGES AND STORED SUBPROGRAMS

EXECUTE PREVILEGE


202

 For stored subprograms and packages the relevant privilege is EXECUTE.
 If user A had the procedure called emp_proc then user A grants execute privilege
on procedure to user B with the following command.
SQL> Grant execute on emp_proc to user B.
 Then user B can run the procedure by issuing
SQL> Exec user A.emp_proc

userA created the following procedure


cursor is select *from student1;
BEGIN

for v in c loop
insert into student2 values(v.no,v.name,v.marks);
end loop;
END P;

userA granted execute privilege to userB using
SQL> grant execute on p to userB

Then userB executed the procedure
SQL> Exec userA.p

If suppose userB also having student2 table then which table will populate whether
userA’s or userB’s.

The answer is userA’s student2 table only because by default the procedure will execute
under the privlige set of its owner.
The above procedure is known as definer’s procedure.

HOW TO POPULATE USER B’s TABLE

 Oracle introduces Invoker’s and Definer’s rights.
 By default it will use the definer’s rights.

 An invoker’s rights routine can be created by using AUTHID clause to populate the
userB’s table.


203

 It is valid for stand-alone subprograms, package specifications, and object type
specifications only.

userA created the following procedure

CREATE OR REPLACE PROCEDURE P
AUTHID CURRENT_USER IS

cursor is select *from student1;
BEGIN

for v in c loop
insert into student2 values(v.no,v.name,v.marks);
end loop;
END P;

Then grant execute privilege on p to userB.
Executing the procedure by userB, which populates userB’s table.

The above procedure is called invoker’s procedure.
Instead of current_user of authid clause, if you use definer then it will be called definer’
procedure.

STORED SUBPROGRAMS AND ROLES

we have two users saketh and sudha in which saketh has student table and sudha does
not.
Sudha is going to create a procedure based on student table owned by saketh. Before
doing this saketh must grant the permissions on this table to sudha.

SQL> conn saketh/saketh
SQL> grant all on student to sudha;
then sudha can create procedure
SQL> conn sudha/sudha


cursor c is select *from saketh.student;
BEGIN

for v in c loop


204

dbms_output.put_line(‘No = ‘ || v.no);
end loop;
END P;

here procedure will be created.

If the same privilege was granted through a role it wont create the procedure.
Examine the following code

SQL> create role saketh_role;
SQL> grant all on student to saketh_role;
SQL> grant saketh_role to sudha;
then conn sudha/sudha


cursor c is select *from saketh.student;
BEGIN

for v in c loop
dbms_output.put_line(‘No = ‘ || v.no);
end loop;
END P;

The above code will raise error instead of creating procedure .
This is because of early binding which PL/SQL uses by default in which references are
evaluated in compile time but when you are using a role this will affect immediately.

ISSUES WITH INVOKER’S RIGHTS

 In an invoker’s rights routine, external references in SQL statements will be
resolved using the caller’s privilege set.

 But references in PL/SQL statements are still resolved under the owner’s privilege
set.

TRIGGERS, VIEWS AND INVOKER’S RIGHTS


205

 A database trigger will always be executed with definer’s rights and will execute
under the privilege set of the schema that owns the triggering table.

 This is also true for PL/SQL function that is called from a view. In this case, the
function will execute under the privilege set of the view’s owner.

PACKAGES


206

A package is a container for related objects. It has specification and body. Each of
them is stored separately in data dictionary.

PACKAGE SYNTAX

Create or replace package <package_name> is
-- package specification includes subprograms signatures, cursors and global or
public variables.
End <package_name>;

Create or replace package body <package_name> is
-- package body includes body for all the subprograms declared in the spec, private
Variables and cursors.
Begin
-- initialization section
Exception
-- Exception handling seciton
End <package_name>;

IMPORTANT POINGS ABOUT PACKAGES

 The first time a packaged subprogram is called or any reference to a packaged
variable or type is made, the package is instantiated.
 Each session will have its own copy of packaged variables, ensuring that two
sessions executing subprograms in the same package use different memory
locations.
 In many cases initialization needs to be run the first time the package is
instantiated within a session. This can be done by adding initialization section to
the package body after all the objects.
 Packages are stored in the data dictionary and can not be local.
 Packaged subprograms has an advantage over stand alone subprogram.

 When ever any reference to package, the whole package p-code was stored in
shared pool of SGA.
 Package may have local subprograms.
 You can include authid clause inside the package spec not in the body.


207

 The execution section of a package is know as initialization section.
 You can have an exception section at the bottom of a package body.
 Packages subprograms are not invalidated.

COMPILING PACKAGES

 SQL> Alter package PKG compile;

 SQL> Alter package PKG compile specification;

 SQL> Alter package PKG compile body;

PACKAGE DEPENDENCIES

 The package body depends on the some objects and the package header.
 The package header does not depend on the package body, which is an advantage
of packages.
 We can change the package body with out changing the header.

PACKAGE RUNTIME STATE

Package runtime state is differ for the following packages.
 Serially reusable packages
 Non serially reusable packages

SERIALLY REUSABLE PACKAGES

To force the oracle to use serially reusable version then include PRAGMA SERIALLY_REUSABLE
in both package spec and body, Examine the following package.

CREATE OR REPLACE PACKAGE PKG IS

pragma serially_reusable;
procedure emp_proc;
END PKG;

CREATE OR REPLACE PACKAGE BODY PKG IS

pragma serially_reusable;


208

cursor c is select ename from emp;
PROCEDURE EMP_PROC IS

v_ename emp.ename%type;
v_flag boolean := true;
v_numrows number := 0;
BEGIN

if not c%isopen then
open c;
end if;
while v_flag loop
fetch c into v_ename;
v_numrows := v_numrows + 1;
if v_numrows = 5 then
v_flag := false;
end if;
dbms_output.put_line('Ename = ' || v_ename);
end loop;
END EMP_PROC;
END PKG;

SQL> exec pkg.emp_proc
Ename = SMITH
Ename = ALLEN
Ename = WARD
Ename = JONES
Ename = MARTIN

Ename = SMITH
Ename = ALLEN
Ename = WARD
Ename = JONES
Ename = MARTIN


209

 The above package displays the same output for each execution even though the
cursor is not closed.
 Because the serially reusable version resets the state of the cursor each time it was
called.

NON SERIALL Y REUSABLE PACKAGES

This is the default version used by the oracle, examine the following package.


procedure emp_proc;
END PKG;


cursor c is select ename from emp;
PROCEDURE EMP_PROC IS

v_ename emp.ename%type;
v_flag boolean := true;
v_numrows number := 0;
BEGIN

if not c%isopen then
open c;
end if;
while v_flag loop
fetch c into v_ename;
v_numrows := v_numrows + 1;
if v_numrows = 5 then
v_flag := false;
end if;
dbms_output.put_line('Ename = ' || v_ename);
end loop;
END EMP_PROC;
END PKG;

Ename = SMITH
Ename = ALLEN


210

Ename = WARD
Ename = JONES
Ename = MARTIN


Ename = BLAKE
Ename = CLARK
Ename = SCOTT
Ename = KING
Ename = TURNER

 The above package displays the different output for each execution even though
the cursor is not closed.
 Because the non-serially reusable version remains the state of the cursor over
database calls.

DEPENDENCIES OF PACKAGE RUNTIME STATE

Dependencies can exists between package state and anonymous blocks.
Examine the following program

Create this package in first session

v number := 5;
procedure p;
END PKG;

PROCEDURE P IS
BEGIN

dbms_output.put_line('v = ' || v);
v := 10;
dbms_output.put_line('v = ' || v);
END P;
END PKG;


211

Connect to second session, run the following code.

BEGIN

pkg.p;
END;

The above code wil work.

Go back to first session and recreate the package using create.
Then connect to second session and run the following code again.

BEGIN

pkg.p;
END;

This above code will not work because of the following.

 The anonymous block depends on pkg. This is compile time dependency.
 There is also a runtime dependency on the packaged variables, since each session
has its own copy of packaged variables.
 Thus when pkg is recompiled the runtime dependency is followed, which
invalidates the block and raises the oracle error.
 Runtime dependencies exist only on package state. This includes variables and
cursors declared in a package.
 If the package had no global variables, the second execution of the anonymous
block would have succeeded.

PURITY LEVELS

In general, calls to subprograms are procedural, they cannot be called from SQL
statements. However, if a stand-alone or packaged function meets certain restrictions, it
can be called during execution of a SQL statement.

User-defined functions are called the same way as built-in functions but it must meet
different restrictions. These restrictions are defined in terms of purity levels.

There are four types of purity levels.


212

WNDS -- Writes No Database State
RNDS -- Reads No Database State
WNPS -- Writes No Package State
RNPS -- Reads No Package State

In addition to the preceding restrictions, a user-defined function must also meet the
following requirements to be called from a SQL statement.

 The function has to be stored in the database, either stand-alone or as part of a
package.
 The function can take only in parametes.

 The formal parameters must use only database types, not PL/SQL types such as
boolean or record.
 The return type of the function must also be a database type.
 The function must not end the current transaction with commit or rollback, or
rollback to a savepoint prior to the function execution.
 It also must not issue any alter session or alter system commands.

RESTRICT_REFERENCES

For packaged functions, however, the RESTRICT_REFERENCES pragma is required to specify
the purity level of a given function.

Syntax:
PRAGMA RESTRICT_REFERENCES(subprogram_name or package_name, WNDS [,WNPS]
[,RNDS] [,RNPS]);

Ex:

function fun1 return varchar;
pragma restrict_references(fun1,wnds);
pragma restrict_references(fun2,wnds);
END PKG;


FUNCTION FUN1 return varchar IS


213

BEGIN

update dept set deptno = 11;
return 'hello';
END FUN1;

BEGIN

update dept set dname ='aa';
return 'hello';
END FUN2;
END PKG;

The above package body will not created, it will give the following erros.

PLS-00452: Subprogram 'FUN1' violates its associated pragma


BEGIN

return 'hello';
END FUN1;

BEGIN

return 'hello';
END FUN2;
END PKG;

Now the package body will be created.

DEFAULT

If there is no RESTRICT_REFERENCES pragma associated with a given packaged function, it
will not have any purity level asserted. However, you can change the default purity level
for a package. The DEFAULT keyword is used instead of the subprogram name in the
pragma.

Ex:


214

pragma restrict_references(default,wnds);
END PKG;


BEGIN

return 'hello';
END FUN1;

BEGIN

return 'hello';
END FUN2;
END PKG;

The above package body will not created, it will give the following erros because the
pragma will apply to all the functions.



BEGIN

return 'hello';
END FUN1;

BEGIN

return 'hello';
END FUN2;
END PKG;

Now the package body will be created.


215

TRUST

If the TRUST keyword is present, the restrictions listed in the pragma are not enforced.
Rather, they are trusted to be true.

Ex:

pragma restrict_references(fun1,wnds,trust);
pragma restrict_references(fun2,wnds,trust);
END PKG;


BEGIN

return 'hello';
END FUN1;

BEGIN

return 'hello';
END FUN2;
END PKG;

The above package will be created successfully.

IMPORTANT POINTS ABOUT RESTRICT_REFERENCES

 This pragma can appear anywhere in the package specification, after the function
declaration.
 It can apply to only one function definition.
 For overload functions, the pragma applies to the nearest definition prior to the
Pragma.
 This pragma is required only for packages functions not for stand-alone functions.


216

 The Pragma can be declared only inside the package specification.
 The pragma is checked at compile time, not runtime.

 It is possible to specify without any purity levels when trust or combination of
default and trust keywords are present.

PINNING IN THE SHARED POOL

The shared pool is the portion of the SGS that contains, among other things, the p-code of
compiled subprograms as they are run. The first time a stored a store subprogram is
called, the p-code is loaded from disk into the shared pool. Once the object is no longer
referenced, it is free to be aged out. Objects are aged out of the shared pool using an
LRU(Least Recently Used) algorithm.

The DBMS_SHARED_POOL package allows you to pin objects in the shared pool. When an
object is pinned, it will never be aged out until you request it, no matter how full the pool
gets or how often the object is accessed. This can improve performance, as it takes time
to reload a package from disk.

DBMS_SHARED_POOL has four procedures

 KEEP
 UNKEEP
 SIZES
 ABORTED_REQUEST_THRESHOLD

KEEP

The DBMS_SHARED_POOL.KEEP procedure is used to pin objects in the pool.

Syntax:
PROCEDURE KEEP(object_name varchar2,flag char default ‘P’);

Here the flag represents different types of flag values for different types of objects.

P -- Package, function or procedure
Q -- Sequence


217

R -- Trigger
C -- SQL Cursor
T -- Object type
JS -- Java source
JC -- Java class
JR -- Java resource
JD -- Java shared data

UNKEEP

UNKEEP is the only way to remove a kept object from the shared pool, without restarting
the database. Kept objects are never aged out automatically.

Syntax:
PROCEDURE UNKEEP(object_name varchar2, flag char default ‘P’);

SIZES

SIZES will echo the contents of the shared pool to the screen.

Syntax:
PROCEDURE SIZES(minsize number);
Objects with greater than the minsize will be returned. SIZES uses DBMS_OUTPUT to return
the data.

ABORTED_REQUEST_THRESHOLD

When the database determines that there is not enough memory in the shared pool to
satisfy a given request, it will begin aging objects out until there is enough memory. It
enough objects are aged out, this can have a performance impact on other database
sessions. The ABORTED_REQUEST_THRESHOLD can be used to remedy this.

Syntax:
PROCEDURE ABORTED_REQUEST_THRESHOLD(threshold_size number);


218

Once this procedure is called, oracle will not start aging objects from the pool unless at
least threshold_size bytes is needed.
DATA MODEL FOR SUBPROGRAMS AND PACKAGES

 USER_OBJECTS
 USER_SOURCE
 USER_ERRORS
 DBA_OBJECTS
 DBA_SOURCE
 DBA_ERRORS
 ALL_OBJECTS
 ALL_SOURCE
 ALL_ERRORS


219

CURSORS

Cursor is a pointer to memory location which is called as context area which contains the
information necessary for processing, including the number of rows processed by the
statement, a pointer to the parsed representation of the statement, and the active set
which is the set of rows returned by the query.

Cursor contains two parts

 Header
 Body

Header includes cursor name, any parameters and the type of data being loaded.
Body includes the select statement.

Ex:
Cursor c(dno in number) return dept%rowtype is select *from dept;
In the above
Header – cursor c(dno in number) return dept%rowtype
Body – select *from dept

CURSOR TYPES

 Implicit (SQL)

 Explicit
 Parameterized cursors
 REF cursors

CURSOR STAGES

 Open
 Fetch


220

 Close

CURSOR ATTRIBUTES

 %found
 %notfound
 %rowcount
 %isopen
 %bulk_rowcount
 %bulk_exceptions

CURSOR DECLERATION

Syntax:
Cursor <cursor_name> is select statement;

Ex:
Cursor c is select *from dept;

CURSOR LOOPS

 Simple loop
 While loop
 For loop

SIMPLE LOOP

Syntax:
Loop
Fetch <cursor_name> into <record_variable>;
Exit when <cursor_name> % notfound;
<statements>;
End loop;


221

Ex:
DECLARE

cursor c is select * from student;
v_stud student%rowtype;
BEGIN

open c;
loop
fetch c into v_stud;
exit when c%notfound;
dbms_output.put_line('Name = ' || v_stud.name);
end loop;
close c;
END;

Output:
Name = saketh
Name = srinu
Name = satish
Name = sudha

WHILE LOOP

Syntax:
While <cursor_name> % found loop
Fetch <cursor_name> nto <record_variable>;
<statements>;
End loop;

Ex:
DECLARE

v_stud student%rowtype;
BEGIN

open c;
while c%found loop


222

end loop;
close c;
END;

Output:

Name = saketh
Name = srinu
Name = satish
Name = sudha

FOR LOOP

Syntax:
for <record_variable> in <cursor_name> loop
<statements>;
End loop;

Ex:
DECLARE

BEGIN

for v_stud in c loop
end loop;
END;

Output:

Name = saketh
Name = srinu
Name = satish
Name = sudha

PARAMETARIZED CURSORS


223

 This was used when you are going to use the cursor in more than one place with
different values for the same where clause.

 Cursor parameters must be in mode.
 Cursor parameters may have default values.
 The scope of cursor parameter is within the select statement.

Ex:
DECLARE

cursor c(dno in number) is select * from dept where deptno = dno;
v_dept dept%rowtype;
BEGIN

open c(20);
loop
fetch c into v_dept;
dbms_output.put_line('Dname = ' || v_dept.dname || ' Loc = ' || v_dept.loc);
end loop;
close c;
END;

Output:

Dname = RESEARCH Loc = DALLAS

PACKAGED CURSORS WITH HEADER IN SPEC AND BODY IN PACKAGE BODY

 cursors declared in packages will not close automatically.
 In packaged cursors you can modify the select statement without making any
changes to the cursor header in the package specification.

 Packaged cursors with must be defined in the package body itself, and then use it
as global for the package.
 You can not define the packaged cursor in any subprograms.
 Cursor declaration in package with out body needs the return clause.

Ex1:


224

cursor c return dept%rowtype is select * from dept;
procedure proc is
END PKG;

CREATE OR REPLACE PAKCAGE BODY PKG IS

cursor c return dept%rowtype is select * from dept;
PROCEDURE PROC IS
BEGIN

for v in c loop
dbms_output.put_line('Deptno = ' || v.deptno || ' Dname = ' ||
v.dname || ' Loc = ' || v.loc);
end loop;
END PROC;
END PKG;

Output:
SQL> exec pkg.proc
Deptno = 10 Dname = ACCOUNTING Loc = NEW YORK
Deptno = 20 Dname = RESEARCH Loc = DALLAS
Deptno = 30 Dname = SALES Loc = CHICAGO
Deptno = 40 Dname = OPERATIONS Loc = BOSTON

Ex2:
CREATE OR REPLACE PAKCAGE BODY PKG IS

cursor c return dept%rowtype is select * from dept where deptno > 20;
PROCEDURE PROC IS
BEGIN

for v in c loop
dbms_output.put_line('Deptno = ' || v.deptno || ' Dname = ' ||
v.dname || ' Loc = ' || v.loc);
end loop;
END PROC;
END PKG;

Output:

SQL> exec pkg.proc


225


REF CURSORS AND CURSOR VARIABLES

 This is unconstrained cursor which will return different types depends upon the
user input.
 Ref cursors can not be closed implicitly.

 Ref cursor with return type is called strong cursor.
 Ref cursor with out return type is called weak cursor.
 You can declare ref cursor type in package spec as well as body.
 You can declare ref cursor types in local subprograms or anonymous blocks.
 Cursor variables can be assigned from one to another.

 You can declare a cursor variable in one scope and assign another cursor variable
with different scope, then you can use the cursor variable even though the
assigned cursor variable goes out of scope.
 Cursor variables can be passed as a parameters to the subprograms.
 Cursor variables modes are in or out or in out.
 Cursor variables can not be declared in package spec and package body (excluding
subprograms).
 You can not user remote procedure calls to pass cursor variables from one server to
another.
 Cursor variables can not use for update clause.
 You can not assign nulls to cursor variables.
 You can not compare cursor variables for equality, inequality and nullity.

Ex:
CREATE OR REPLACE PROCEDURE REF_CURSOR(TABLE_NAME IN VARCHAR) IS

type t is ref cursor;
c t;
v_dept dept%rowtype;
type r is record(ename emp.ename%type,job emp.job%type,sal emp.sal%type);
v_emp r;
v_stud student.name%type;


226

BEGIN

if table_name = 'DEPT' then
open c for select * from dept;
elsif table_name = 'EMP' then
open c for select ename,job,sal from emp;
elsif table_name = 'STUDENT' then
open c for select name from student;
end if;
loop
if table_name = 'DEPT' then
fetch c into v_dept;
dbms_output.put_line('Deptno = ' || v_dept.deptno || ' Dname = ' ||
v_dept.dname || ' Loc = ' || v_dept.loc);
elsif table_name = 'EMP' then
fetch c into v_emp;
dbms_output.put_line('Ename = ' || v_emp.ename || ' Job = ' || v_emp.job
|| ' Sal = ' || v_emp.sal);
elsif table_name = 'STUDENT' then
dbms_output.put_line('Name = ' || v_stud);
end if;
end loop;
close c;
END;

Output:
SQL> exec ref_cursor('DEPT')

Deptno = 10 Dname = ACCOUNTING Loc = NEW YORK
Deptno = 20 Dname = RESEARCH Loc = DALLAS


227

SQL> exec ref_cursor('EMP')

Ename = SMITH Job = CLERK Sal = 800
Ename = ALLEN Job = SALESMAN Sal = 1600
Ename = WARD Job = SALESMAN Sal = 1250
Ename = JONES Job = MANAGER Sal = 2975
Ename = MARTIN Job = SALESMAN Sal = 1250
Ename = BLAKE Job = MANAGER Sal = 2850
Ename = CLARK Job = MANAGER Sal = 2450
Ename = SCOTT Job = ANALYST Sal = 3000
Ename = KING Job = PRESIDENT Sal = 5000
Ename = TURNER Job = SALESMAN Sal = 1500
Ename = ADAMS Job = CLERK Sal = 1100
Ename = JAMES Job = CLERK Sal = 950
Ename = FORD Job = ANALYST Sal = 3000
Ename = MILLER Job = CLERK Sal = 1300

SQL> exec ref_cursor('STUDENT')

Name = saketh
Name = srinu
Name = satish
Name = sudha

CURSOR EXPRESSIONS

 You can use cursor expressions in explicit cursors.
 You can use cursor expressions in dynamic SQL.
 You can use cursor expressions in REF cursor declarations and variables.
 You can not use cursor expressions in implicit cursors.
 Oracle opens the nested cursor defined by a cursor expression implicitly as soon as
it fetches the data containing the cursor expression from the parent or outer
cursor.
 Nested cursor closes if you close explicitly.


228

 Nested cursor closes whenever the outer or parent cursor is executed again or
closed or canceled.
 Nested cursor closes whenever an exception is raised while fetching data from a
parent cursor.
 Cursor expressions can not be used when declaring a view.
 Cursor expressions can be used as an argument to table function.
 You can not perform bind and execute operations on cursor expressions when
using the cursor expressions in dynamic SQL.

USING NESTED CURSORS OR CURSOR EXPRESSIONS

Ex:
DECLARE

cursor c is select ename,cursor(select dname from dept d where e.empno =
d.deptno) from emp e;
c1 t;
c2 t;
v1 emp.ename%type;
v2 dept.dname%type;
BEGIN

open c;
loop
fetch c1 into v1;
exit when c1%notfound;
fetch c2 into v2;
exit when c2%notfound;
dbms_output.put_line('Ename = ' || v1 || ' Dname = ' || v2);
end loop;
end loop;
close c;
END;

CURSOR CLAUSES

 Return


229

 For update
 Where current of
 Bulk collect

RETURN

Cursor c return dept%rowtype is select *from dept;
Or
Cursor c1 is select *from dept;
Cursor c return c1%rowtype is select *from dept;
Or
Type t is record(deptno dept.deptno%type, dname dept.dname%type);
Cursor c return t is select deptno, dname from dept;

FOR UPDATE AND WHERE CURRENT OF

Normally, a select operation will not take any locks on the rows being accessed. This will
allow other sessions connected to the database to change the data being selected. The
result set is still consistent. At open time, when the active set is determined, oracle takes
a snapshot of the table. Any changes that have been committed prior to this point are
reflected in the active set. Any changes made after this point, even if they are committed,
are not reflected unless the cursor is reopened, which will evaluate the active set again.

However, if the FOR UPDATE caluse is pesent, exclusive row locks are taken on the rows in
the active set before the open returns. These locks prevent other sessions from changing
the rows in the active set until the transaction is committed or rolled back. If another
session already has locks on the rows in the active set, then SELECT … FOR UPDATE operation
will wait for these locks to be released by the other session. There is no time-out for this
waiting period. The SELECT…FOR UPDATE will hang until the other session releases the lock.
To handle this situation, the NOWAIT clause is available.

Syntax:
Select …from … for update of column_name [wait n];


230

If the cursor is declared with the FOR UPDATE clause, the WHERE CURRENT OF clause can
be used in an update or delete statement.

Syntax:
Where current of cursor;

Ex:
DECLARE

cursor c is select * from dept for update of dname;
BEGIN

for v in c loop
update dept set dname = 'aa' where current of c;
commit;
end loop;
END;

BULK COLLECT

 This is used for array fetches
 With this you can retrieve multiple rows of data with a single roundtrip.
 This reduces the number of context switches between the pl/sql and sql engines.
 Reduces the overhead of retrieving data.
 You can use bulk collect in both dynamic and static sql.
 You can use bulk collect in select, fetch into and returning into clauses.
 SQL engine automatically initializes and extends the collections you reference in
the bulk collect clause.
 Bulk collect operation empties the collection referenced in the into clause before
executing the query.
 You can use the limit clause of bulk collect to restrict the no of rows retrieved.
 You can fetch into multible collections with one column each.

 Using the returning clause we can return data to the another collection.

BULK COLLECT IN FETCH

Ex:


231

DECLARE

Type t is table of dept%rowtype;
nt t;
BEGIN

Open c;
Fetch c bulk collect into nt;
Close c;
For i in nt.first..nt.last loop
dbms_output.put_line('Dname = ' || nt(i).dname || ' Loc = ' ||
nt(i).loc);
end loop;
END;

Output:
Dname = ACCOUNTING Loc = NEW YORK
Dname = SALES Loc = CHICAGO
Dname = OPERATIONS Loc = BOSTON

BULK COLLECT IN SELECT

Ex:
DECLARE

Nt t;
BEGIN

Select * bulk collect into nt from dept;
for i in nt.first..nt.last loop
nt(i).loc);
end loop;
END;

Output:


232

Dname = SALES Loc = CHICAGO
Dname = OPERATIONS Loc = BOSTON

LIMIT IN BULK COLLECT

You can use this to limit the number of rows to be fetched.

Ex:
DECLARE

nt t;
BEGIN

Open c;
Fetch c bulk collect into nt limit 2;
Close c;
nt(i).loc);
end loop;
END;

Output:

MULTIPLE FETCHES IN INTO CLAUSE

Ex1:
DECLARE

Type t is table of dept.dname%type;
nt t;
Type t1 is table of dept.loc%type;
nt1 t;
Cursor c is select dname,loc from dept;
BEGIN


233

Open c;
Fetch c bulk collect into nt,nt1;
Close c;
dbms_output.put_line('Dname = ' || nt(i));
end loop;
For i in nt1.first..nt1.last loop
dbms_output.put_line('Loc = ' || nt1(i));
end loop;
END;

Output:
Dname = ACCOUNTING
Dname = RESEARCH
Dname = SALES
Dname = OPERATIONS
Loc = NEW YORK
Loc = DALLAS
Loc = CHICAGO
Loc = BOSTON

Ex2:
DECLARE

type t is table of dept.dname%type;
type t1 is table of dept.loc%type;
nt t;
nt1 t1;
BEGIN

Select dname,loc bulk collect into nt,nt1 from dept;
for i in nt.first..nt.last loop
dbms_output.put_line('Dname = ' || nt(i));
end loop;
for i in nt1.first..nt1.last loop
dbms_output.put_line('Loc = ' || nt1(i));
end loop;
END;


234

Output:
Dname = ACCOUNTING
Dname = RESEARCH
Dname = SALES
Dname = OPERATIONS
Loc = NEW YORK
Loc = DALLAS
Loc = CHICAGO
Loc = BOSTON

RETURNING CLAUSE IN BULK COLLECT

You can use this to return the processed data to the ouput variables or typed variables.

Ex:
DECLARE

type t is table of number(2);
nt t := t(1,2,3,4);
type t1 is table of varchar(2);
nt1 t1;
type t2 is table of student%rowtype;
nt2 t2;
BEGIN

select name bulk collect into nt1 from student;
forall v in nt1.first..nt1.last
update student set no = nt(v) where name = nt1(v) returning
no,name,marks bulk collect into nt2;
for v in nt2.first..nt2.last loop
dbms_output.put_line('Marks = ' || nt2(v));
end loop;
END;

Output:
Marks = 100
Marks = 200


235

Marks = 300
Marks = 400

POINTS TO REMEMBER

 Cursor name can be up to 30 characters in length.
 Cursors declared in anonymous blocks or subprograms closes automatically when
that block terminates execution.
 %bulk_rowcount and %bulk_exceptions can be used only with forall construct.
 Cursor declarations may have expressions with column aliases.
 These expressions are called virtual columns or calculated columns.


236

SQL IN PL/SQL

The only statements allowed directly in pl/sql are DML and TCL.

BINDING

Binding a variable is the process of identifying the storage location associated with an
identifier in the program.

Types of binding

 Early binding
 Late binding

 Binding during the compiled phase is early binding.
 Binding during the runtime phase is late binding.
 In early binding compile phase will take longer because of binding work but the
execution is faster.
 In late binding it will shorten the compile phase but lengthens the execution time.

 PL/SQL by default uses early binding.

 Binding also involves checking the database for permissions to access the object
Referenced.

DYNAMIC SQL


237

 If you use DDL in pl/sql it validates the permissions and existence if requires
during compile time which makes invalid.

 We can avoid this by using Dynamic SQL.
 Dynamic SQL allows you to create a SQL statement dynamically at runtime.

Two techniques are available for Dynamic SQL.

 Native Dynamic SQL
 DBMS_SQL package

USING NATIVE DYNAMIC SQL

USING EXECUTE IMMEDIATE

Ex:
BEGIN

Execute immediate ‘create table student(no number(2),name varchar(10))’;
or
Execute immediate (‘create table student(no number(2),name varchar(10))’);
END;

USING EXECUTE IMMEDIATE WITH PL/SQL VARIABLES

Ex:
DECLARE

v varchar(100);
BEGIN

v := 'create table student(no number(2),name varchar(10))';
execute immediate v;
END;

USING EXECUTE IMMEDIATE WITH BIND VARIABLES AND USING CLAUSE

Ex:
DECLARE

v varchar(100);
BEGIN


238

v := 'insert into student values(:v1,:v2,:v3)';
execute immediate v using 6,'f',600;
END;

EXECUTING QUERIES WITH OPEN FOR AND USING CLAUSE

Ex:
CREATE OR REPLACE PROCEDURE P(smarks in number) IS
s varchar(100) := 'select *from student where marks > :m';
c t;
v student%rowtype;
BEGIN

open c for s using smarks;
loop
fetch c into v;
dbms_output.put_line('Student Marks = ' || v.marks);
end loop;
close c;
END;

Output:
SQL> exec p(100)

Student Marks = 200
Student Marks = 300
Student Marks = 400

QUERIES WITH EXECUTE IMMEDIATE

Ex:
DECLARE

d_name dept.dname%type;
lc dept.loc%type;
v varchar(100);
BEGIN


239

v := 'select dname from dept where deptno = 10';
execute immediate v into d_name;
dbms_output.put_line('Dname = '|| d_name);
v := 'select loc from dept where dname = :dn';
execute immediate v into lc using d_name;
dbms_output.put_line('Loc = ' || lc);
END;

Output:
Dname = ACCOUNTING
Loc = NEW YORK
VARIABLE NAMES

Ex:
DECLARE

Marks number(3) := 100;
BEGIN

Delete student where marks = marks; -- this will delete all the rows in the
-- student table
END;

This can be avoided by using the labeled blocks.

<<my_block>>
DECLARE

Marks number(3) := 100;
BEGIN

Delete student where marks = my_block.marks; -- delete rows which has
-- a marks of 100
END;

GETTING DATA INTO PL/SQL VARIABLES

Ex:
DECLARE

V1 number;
V2 varchar(2);
BEGIN


240

Select no,name into v1,v2 from student where marks = 100;
END;

DML AND RECORDS

Ex:
CREATE OR REPLACE PROCEDURE P(srow in student%rowtype) IS
BEGIN

insert into student values srow;
END P;

DECLARE

s student%rowtype;
BEGIN

s.no := 11;
s.name := 'aa';
s.marks := 100;
p(s);
END;

RECORD BASED INSERTS

Ex:
DECLARE

srow student%rowtype;
BEGIN

srow.no := 7;
srow.name := 'cc';
srow.marks := 500;
insert into student values srow;
END;

RECORD BASED UPDATES

Ex:
DECLARE

BEGIN


241

srow.no := 6;
srow.name := 'cc';
srow.marks := 500;
update student set row=srow where no = srow.no;
END;

USING RECORDS WITH RETURNING CLAUSE

Ex:
DECLARE

sreturn student%rowtype;
BEGIN

srow.no := 8;
srow.name := 'dd';
srow.marks := 500;
insert into student values srow returning no,name,marks into sreturn;
dbms_output.put_line('No = ' || sreturn.no);
dbms_output.put_line('No = ' || sreturn.name);
dbms_output.put_line('No = ' || sreturn.marks);
END;

Output:
No = 8
No = dd
No = 500

USING DBMS_SQL PACKAGE

DBMS_SQL is used to execute dynamic SQL from with in PL/SQL. Unlike native dynamic
SQL, it is not built directly into the language, and thus is less efficient. The DBMS_SQL
package allows you to directly control the processing of a statement within a cursor,
with operations such as opening and closing a cursor, parsing a statement, binding
input variable, and defining output variables.

Ex1:


242

DECLARE

cursor_id number;
flag number;
v_stmt varchar(50);
BEGIN

cursor_id := dbms_sql.open_cursor;
v_stmt := 'create table stud(sno number(2),sname varchar(10))';
dbms_sql.parse(cursor_id,v_stmt,dbms_sql.native);
flag := dbms_sql.execute(cursor_id);
dbms_sql.close_cursor(cursor_id);
dbms_output.put_line('Table created');
END;

Output:

Table created

SQL> desc stud
Name Null? Type
----------------------------------------------------------------- -------- --------
SNO NUMBER(2)
SNAME VARCHAR2(10)

Ex2:

CREATE OR REPLACE PROCEDURE DBMS_SQL_PROC(v1 student.no%type,
v2 student.marks%type) is
cursor_id number;
flag number;
v_update varchar(50);
BEGIN

cursor_id := dbms_sql.open_cursor;
v_update := 'update student set marks = :smarks where no = :sno';
dbms_sql.parse(cursor_id,v_update,dbms_sql.native);
dbms_sql.bind_variable(cursor_id,':sno',v1);
dbms_sql.bind_variable(cursor_id,':smarks',v2);


243

flag := dbms_sql.execute(cursor_id);
dbms_sql.close_cursor(cursor_id);
END DBMS_SQL_PROC;

Output:

SQL> select * from student; -- before execution

NO NA MARKS
---- ------ -- ----------
1 a 100
2 b 200
3 c 300

SQL> exec dbms_sql_proc(2,222)

SQL> select * from student; -- after execution

NO NA MARKS
---- ------ -- ----------
1 a 100
2 b 222
3 c 300

FORALL STATEMENT

This can be used to get the data from the database at once by reducting the number of
context switches which is a transfer of control between PL/SQL and SQL engine.

Syntax:
Forall index_var in
[ Lower_bound..upper_bound |
Indices of indexing_collection |
Values of indexing_collection ]
SQL statement;


244

FORALL WITH NON-SEQUENTIAL ARRAYS

Ex:
DECLARE

type t is table of student.no%type index by binary_integer;
ibt t;
BEGIN

ibt(1) := 1;
ibt(10) := 2;
forall i in ibt.first..ibt.last
update student set marks = 900 where no = ibt(i);
END;

The above program will give error like ‘element at index [2] does not exists.
You can rectify it in one of the two following ways.

USGAGE OF INDICES OF TO AVOID THE ABOVE BEHAVIOUR

This will be used when you have a collection whose defined rows specify which rows in
the binding array you would like to processed.

Ex:
DECLARE

ibt t;
type t1 is table of boolean index by binary_integer;
ibt1 t1;
BEGIN

ibt(1) := 1;
ibt(10) := 2;
ibt(100) := 3;
ibt1(1) := true;
ibt1(10) := true;
ibt1(100) := true;
forall i in indices of ibt1
END;


245

Ouput:

SQL> select * from student -- before execution

NO NA MARKS
---------- ------------
1 a 100
2 b 200
3 c 300
SQL> select * from student -- after execution

NO NA MARKS
---------- ------------
1 a 900
2 b 900
3 c 900

USGAGE OF VALUES OF TO AVOID THE ABOVE BEHAVIOUR

This will be used when you have a collection of integers whose content identifies the
position in the binding array that you want to be processed by the FORALL statement.

Ex:
DECLARE

ibt t;
type t1 is table of pls_integer index by binary_integer;
ibt1 t1;
BEGIN

ibt(1) := 1;
ibt(10) := 2;
ibt(100) := 3;
ibt1(11) := 1;
ibt1(15) := 10;
ibt1(18) := 100;
forall i in values of ibt1


246

END;

Ouput:

SQL> select * from student -- before execution

NO NA MARKS
---------- ------------
1 a 100
2 b 200
3 c 300

SQL> select * from student -- after execution

NO NA MARKS
---------- ------------
1 a 900
2 b 900
3 c 900

POINTS ABOUT BULK BINDS

 Passing the entire PL/SQL table to the SQL engine in one step is known as bulk
bind.
 Bulk binds are done using the forall statement.
 If there is an error processing one of the rows in bulk DML operation, only that
row is rolled back.

POINTS ABOUT RETURING CLAUSE

 This will be used only with DML statements to return data into PL/SQL variables.
 This will be useful in situations like , when performing insert or update or delete if
you want to know the data of the table which has been effected by the DML.

 With out going for another SELECT using RETURNING clause we will get the data which
will avoid a call to RDBMS kernel.


247

COLLECTIONS

Collections are also composite types, in that they allow you to treat several variables as a
unit. A collection combines variables of the same type.

TYPES
 Varrays
 Nested tables

 Index - by tables (Associate arrays)

VARRAYS

A varray is datatype very similar to an array. A varray has a fixed limit on its size,
specified as part of the declaration. Elements are inserted into varray starting at index 1,
up to maximum lenth declared in the varray type. The maximum size of the varray is 2
giga bytes.

Syntax:
Type <type_name> is varray | varying array (<limit>) of <element_type>;

Ex1:
DECLARE

type t is varray(10) of varchar(2);
va t := t('a','b','c','d');
flag boolean;
BEGIN


248

dbms_output.put_line('Limit = ' || va.limit);
dbms_output.put_line('Count = ' || va.count);
dbms_output.put_line('First Index = ' || va.first);
dbms_output.put_line('Last Index = ' || va.last);
dbms_output.put_line('Next Index = ' || va.next(2));
dbms_output.put_line('Previous Index = ' || va.prior(3));
dbms_output.put_line('VARRAY ELEMENTS');
for i in va.first..va.last loop
dbms_output.put_line('va[' || i || '] = ' || va(i));
end loop;
flag := va.exists(3);
if flag = true then
dbms_output.put_line('Index 3 exists with an element ' || va(3));
else
dbms_output.put_line('Index 3 does not exists');
end if;
va.extend;
dbms_output.put_line('After extend of one index, Count = ' || va.count);
if flag = true then
else
end if;
if flag = true then
else
end if;
va.extend(2);
dbms_output.put_line('After extend of two indexes, Count = ' || va.count);


249

end loop;
va(5) := 'e';
va(6) := 'f';
va(7) := 'g';
dbms_output.put_line('AFTER ASSINGNING VALUES TO EXTENDED ELEMENTS,
VARRAY ELEMENTS');

end loop;
va.extend(3,2);
dbms_output.put_line('After extend of three indexes, Count = ' || va.count);
end loop;
va.trim;
dbms_output.put_line('After trim of one index, Count = ' || va.count);
va.trim(3);
dbms_output.put_line('After trim of three indexs, Count = ' || va.count);
dbms_output.put_line('AFTER TRIM, VARRAY ELEMENTS');
end loop;
va.delete;
dbms_output.put_line('After delete of entire varray, Count = ' || va.count);
END;

Output:
Limit = 10
Count = 4
First Index = 1
Last Index = 4
Next Index = 3
Previous Index = 2
VARRAY ELEMENTS
va[1] = a


250

va[2] = b
va[3] = c
va[4] = d
Index 3 exists with an element c
After extend of one index, Count = 5
Index 5 exists with an element
Index 6 does not exists
After extend of two indexes, Count = 7
VARRAY ELEMENTS
va[1] = a
va[2] = b
va[3] = c
va[4] = d
va[5] =
va[6] =
va[7] =
AFTER ASSINGNING VALUES TO EXTENDED ELEMENTS, VARRAY ELEMENTS
va[1] = a
va[2] = b
va[3] = c
va[4] = d
va[5] = e
va[6] = f
va[7] = g
After extend of three indexes, Count = 10
VARRAY ELEMENTS
va[1] = a
va[2] = b
va[3] = c
va[4] = d
va[5] = e
va[6] = f
va[7] = g
va[8] = b
va[9] = b


251

va[10] = b
After trim of one index, Count = 9
After trim of three indexs, Count = 6
AFTER TRIM, VARRAY ELEMENTS
va[1] = a
va[2] = b
va[3] = c
va[4] = d
va[5] = e
va[6] = f
After delete of entire varray, Count = 0

Ex2:
DECLARE

type t is varray(4) of student%rowtype;
va t := t(null,null,null,null);
BEGIN

for i in 1..va.count loop
select * into va(i) from student where sno = i;
dbms_output.put_line('Sno = ' || va(i).sno || ' Sname = ' || va(i).sname);
end loop;
END;

Output:
Sno = 1 Sname = saketh
Sno = 2 Sname = srinu
Sno = 3 Sname = divya
Sno = 4 Sname = manogni

Ex3:
DECLARE

type t is varray(4) of student.smarks%type;
BEGIN

select smarks into va(i) from student where sno = i;


252

dbms_output.put_line('Smarks = ' || va(i));
end loop;
END;

Output:
Smarks = 100
Smarks = 200
Smarks = 300
Smarks = 400

Ex4:
DECLARE

type r is record(c1 student.sname%type,c2 student.smarks%type);
type t is varray(4) of r;
BEGIN

select sname,smarks into va(i) from student where sno = i;
dbms_output.put_line('Sname = ' || va(i).c1 || ' Smarks = ' || va(i).c2);
end loop;
END;

Output:
Sname = saketh Smarks = 100
Sname = srinu Smarks = 200
Sname = divya Smarks = 300
Sname = manogni Smarks = 400

Ex5:
DECLARE

type t is varray(1) of addr;
va t := t(null);
cursor c is select * from employ;
i number := 1;
BEGIN

for v in c loop
select address into va(i) from employ where ename = v.ename;


253

dbms_output.put_line('Hno = ' || va(i).hno || ' City = ' || va(i).city);
end loop;
END;

Output:
Hno = 11 City = hyd
Hno = 22 City = bang
Hno = 33 City = kochi

Ex6:
DECLARE

va1 t;
va2 t := t();
BEGIN

if va1 is null then
dbms_output.put_line('va1 is null');
else
dbms_output.put_line('va1 is not null');
end if;
if va2 is null then
dbms_output.put_line('va2 is null');
else
dbms_output.put_line('va2 is not null');
end if;
END;

Output:
va1 is null
va2 is not null

NESTED TABLES


254

A nested table is thought of a database table which has no limit on its size. Elements are
inserted into nested table starting at index 1. The maximum size of the varray is 2 giga
bytes.

Syntax:
Type <type_name> is table of <table_type>;

Ex1:
DECLARE

type t is table of varchar(2);
nt t := t('a','b','c','d');
flag boolean;
BEGIN

if nt.limit is null then
dbms_output.put_line('No limit to Nested Tables');
else
dbms_output.put_line('Limit = ' || nt.limit);
end if;
dbms_output.put_line('Count = ' || nt.count);
dbms_output.put_line('First Index = ' || nt.first);
dbms_output.put_line('Last Index = ' || nt.last);
dbms_output.put_line('Next Index = ' || nt.next(2));
dbms_output.put_line('Previous Index = ' || nt.prior(3));
dbms_output.put_line('NESTED TABLE ELEMENTS');
for i in 1..nt.count loop
dbms_output.put_line('nt[' || i || '] = ' || nt(i));
end loop;
flag := nt.exists(3);
if flag = true then
dbms_output.put_line('Index 3 exists with an element ' || nt(3));
else
end if;
nt.extend;
dbms_output.put_line('After extend of one index, Count = ' || nt.count);


255

if flag = true then
else
end if;
if flag = true then
else
end if;
nt.extend(2);
dbms_output.put_line('After extend of two indexes, Count = ' || nt.count);
end loop;
nt(5) := 'e';
nt(6) := 'f';
nt(7) := 'g';
dbms_output.put_line('AFTER ASSINGNING VALUES TO EXTENDED ELEMENTS, NESTED
TABLE ELEMENTS');

end loop;
nt.extend(5,2);
dbms_output.put_line('After extend of five indexes, Count = ' || nt.count);
end loop;
nt.trim;
dbms_output.put_line('After trim of one index, Count = ' || nt.count);
nt.trim(3);
dbms_output.put_line('After trim of three indexs, Count = ' || nt.count);
dbms_output.put_line('AFTER TRIM, NESTED TABLE ELEMENTS');


256

end loop;
nt.delete(1);
dbms_output.put_line('After delete of first index, Count = ' || nt.count);
for i in 2..nt.count+1 loop
end loop;
nt.delete(4);
dbms_output.put_line('After delete of fourth index, Count = ' || nt.count);
for i in 2..3 loop
end loop;
for i in 5..nt.count+2 loop
end loop;
nt.delete;
dbms_output.put_line('After delete of entire nested table, Count = ' ||
nt.count);
END;

Output:
No limit to Nested Tables
Count = 4
First Index = 1
Last Index = 4
Next Index = 3
Previous Index = 2
NESTED TABLE ELEMENTS
nt[1] = a
nt[2] = b
nt[3] = c
nt[4] = d


257

Index 5 exists with an element
After extend of two indexes, Count = 7
nt[1] = a
nt[2] = b
nt[3] = c
nt[4] = d
nt[5] =
nt[6] =
nt[7] =
AFTER ASSINGNING VALUES TO EXTENDED ELEMENTS, NESTED TABLE
ELEMENTS
nt[1] = a
nt[2] = b
nt[3] = c
nt[4] = d
nt[5] = e
nt[6] = f
nt[7] = g
After extend of five indexes, Count = 12
nt[1] = a
nt[2] = b
nt[3] = c
nt[4] = d
nt[5] = e
nt[6] = f
nt[7] = g
nt[8] = b
nt[9] = b
nt[10] = b
nt[11] = b
nt[12] = b


258

After trim of three indexs, Count = 8
AFTER TRIM, NESTED TABLE ELEMENTS
nt[1] = a
nt[2] = b
nt[3] = c
nt[4] = d
nt[5] = e
nt[6] = f
nt[7] = g
nt[8] = b
After delete of first index, Count = 7
nt[2] = b
nt[3] = c
nt[4] = d
nt[5] = e
nt[6] = f
nt[7] = g
nt[8] = b
After delete of fourth index, Count = 6
nt[2] = b
nt[3] = c
nt[5] = e
nt[6] = f
nt[7] = g
nt[8] = b
After delete of entire nested table, Count = 0

Ex2:
DECLARE

type t is table of student%rowtype;
nt t := t(null,null,null,null);
BEGIN



259

select * into nt(i) from student where sno = i;
dbms_output.put_line('Sno = ' || nt(i).sno || ' Sname = ' || nt(i).sname);
end loop;
END;

Output:
Sno = 1 Sname = saketh
Sno = 2 Sname = srinu
Sno = 3 Sname = divya
Sno = 4 Sname = manogni

Ex3:
DECLARE

type t is table of student.smarks%type;
BEGIN

select smarks into nt(i) from student where sno = i;
dbms_output.put_line('Smarks = ' || nt(i));
end loop;
END;

Output:
Smarks = 100
Smarks = 200
Smarks = 300
Smarks = 400

Ex4:
DECLARE

type r is record(c1 student.sname%type,c2 student.smarks%type);
type t is table of r;
BEGIN

select sname,smarks into nt(i) from student where sno = i;
dbms_output.put_line('Sname = ' || nt(i).c1 || ' Smarks = ' || nt(i).c2);


260

end loop;
END;

Output:
Sname = saketh Smarks = 100
Sname = srinu Smarks = 200
Sname = divya Smarks = 300
Sname = manogni Smarks = 400

Ex5:
DECLARE

type t is table of addr;
nt t := t(null);
cursor c is select * from employ;
i number := 1;
BEGIN

for v in c loop
select address into nt(i) from employ where ename = v.ename;
dbms_output.put_line('Hno = ' || nt(i).hno || ' City = ' || nt(i).city);
end loop;
END;

Output:
Hno = 11 City = hyd
Hno = 22 City = bang
Hno = 33 City = kochi

Ex6:
DECLARE

nt1 t;
nt2 t := t();
BEGIN

if nt1 is null then
dbms_output.put_line('nt1 is null');


261

else
dbms_output.put_line('nt1 is not null');
end if;
if nt2 is null then
dbms_output.put_line('nt2 is null');
else
dbms_output.put_line('nt2 is not null');
end if;
END;

Output:
nt1 is null
nt2 is not null

SET OPERATIONS IN NESTED TABLES

You can perform set operations in the nested tables. You can also perform equality
comparisions between nested tables.

Possible operations are

 UNION
 UNION DISTINCT
 INTERSECT

 EXCEPT ( act like MINUS)

Ex:
DECLARE

type t is table of varchar(2);
nt1 t := t('a','b','c');
nt2 t := t('c','b','a');
nt3 t := t('b','c','a','c');
nt4 t := t('a','b','d');
nt5 t;
BEGIN

nt5 := set(nt1);


262

dbms_output.put_line('nt5[ ' || i || ' ] = ' || nt5(i));
end loop;
nt5 := set(nt3);
end loop;
nt5 := nt1 multiset union nt4;
end loop;
nt5 := nt1 multiset union nt3;
end loop;
nt5 := nt1 multiset union distinct nt3;
end loop;
nt5 := nt1 multiset except nt4;
end loop;
nt5 := nt4 multiset except nt1;
end loop;
END;


263

Output:

nt5[ 1 ] = a
nt5[ 2 ] = b
nt5[ 3 ] = c
nt5[ 1 ] = b
nt5[ 2 ] = c
nt5[ 3 ] = a
nt5[ 1 ] = a
nt5[ 2 ] = b
nt5[ 3 ] = c
nt5[ 4 ] = a
nt5[ 5 ] = b
nt5[ 6 ] = d
nt5[ 1 ] = a
nt5[ 2 ] = b
nt5[ 3 ] = c
nt5[ 4 ] = b
nt5[ 5 ] = c
nt5[ 6 ] = a
nt5[ 7 ] = c
nt5[ 1 ] = a
nt5[ 2 ] = b
nt5[ 3 ] = c
nt5[ 1 ] = c
nt5[ 1 ] = d

INDEX-BY TABLES


264

An index-by table has no limit on its size. Elements are inserted into index-by table whose
index may start non-sequentially including negative integers.

Syntax:
Type <type_name> is table of <table_type> index by binary_integer;

Ex:
DECLARE

type t is table of varchar(2) index by binary_integer;
ibt t;
flag boolean;
BEGIN

ibt(1) := 'a';
ibt(-20) := 'b';
ibt(30) := 'c';
ibt(100) := 'd';
if ibt.limit is null then
dbms_output.put_line('No limit to Index by Tables');
else
dbms_output.put_line('Limit = ' || ibt.limit);
end if;
dbms_output.put_line('Count = ' || ibt.count);
dbms_output.put_line('First Index = ' || ibt.first);
dbms_output.put_line('Last Index = ' || ibt.last);
dbms_output.put_line('Next Index = ' || ibt.next(2));
dbms_output.put_line('Previous Index = ' || ibt.prior(3));
dbms_output.put_line('INDEX BY TABLE ELEMENTS');
dbms_output.put_line('ibt[-20] = ' || ibt(-20));
dbms_output.put_line('ibt[1] = ' || ibt(1));
flag := ibt.exists(30);
if flag = true then
dbms_output.put_line('Index 30 exists with an element ' || ibt(30));
else


265

end if;
if flag = true then
dbms_output.put_line('Index 50 exists with an element ' || ibt(30));
else
end if;
ibt.delete(1);
dbms_output.put_line('After delete of first index, Count = ' || ibt.count);
ibt.delete(30);
dbms_output.put_line('After delete of index thirty, Count = ' || ibt.count);
dbms_output.put_line('INDEX BY TABLE ELEMENTS');
dbms_output.put_line('ibt[-20] = ' || ibt(-20));
ibt.delete;
dbms_output.put_line('After delete of entire index-by table, Count = ' ||
ibt.count);
END;

Output:

No limit to Index by Tables
Count = 4
First Index = -20
Last Index = 100
Next Index = 30
Previous Index = 1
INDEX BY TABLE ELEMENTS
ibt[-20] = b
ibt[1] = a
ibt[30] = c
ibt[100] = d


266

After delete of index thirty, Count = 2
INDEX BY TABLE ELEMENTS
ibt[-20] = b
ibt[100] = d
After delete of entire index-by table, Count = 0

DIFFERENCES AMONG COLLECTIONS

 Varrays has limit, nested tables and index-by tables has no limit.
 Varrays and nested tables must be initialized before assignment of elements, in
index-by tables we can directly assign elements.
 Varrays and nested tables stored in database, but index-by tables can not.

 Nested tables and index-by tables are PL/SQL tables, but varrays can not.
 Keys must be positive in case of nested tables and varrays, in case of index-by
tables keys can be positive or negative.

 Referencing nonexistent elements raises SUBSCRIPT_BEYOND_COUNT in both nested
tables and varrays, but in case of index-by tables NO_DATA_FOUND raises.
 Keys are sequential in both nested tables and varrays, non-sequential in index-by
tables.

 Individual indexes can be deleted in both nested tables and index-by tables, but in
varrays can not.

 Individual indexes can be trimmed in both nested tables and varrays, but in index-
by tables can not.
 Individual indexes can be extended in both nested tables and varrays, but in index-
by tables can not.

MULTILEVEL COLLECTIONS

Collections of more than one dimension which is a collection of collections, known as
multilevel collections.

Syntax:
Type <type_name1> is table of <table_type> index by binary_integer;
Type <type_name2> is varray(<limit>) | table | of <type_name1> | index by


267

binary_integer;

Ex1:
DECLARE

type t1 is table of varchar(2) index by binary_integer;
type t2 is varray(5) of t1;
va t2 := t2();
c number := 97;
flag boolean;
BEGIN

va.extend(4);
dbms_output.put_line('Count = ' || va.count);
dbms_output.put_line('Limit = ' || va.limit);
for j in 1..va.count loop
va(i)(j) := chr(c);
c := c + 1;
end loop;
end loop;
dbms_output.put_line('va[' || i || '][' || j || '] = ' || va(i)(j));
end loop;
end loop;
dbms_output.put_line('First index = ' || va.first);
dbms_output.put_line('Last index = ' || va.last);
dbms_output.put_line('Next index = ' || va.next(2));
dbms_output.put_line('Previous index = ' || va.prior(3));
if flag = true then
dbms_output.put_line('Index 2 exists');
else
end if;
va.extend;


268

va(1)(5) := 'q';
va(2)(5) := 'r';
va(3)(5) := 's';
va(4)(5) := 't';
va(5)(1) := 'u';
va(5)(2) := 'v';
va(5)(3) := 'w';
va(5)(4) := 'x';
va(5)(5) := 'y';
dbms_output.put_line('After extend of one index, Count = ' || va.count);
end loop;
end loop;
va.trim;
dbms_output.put_line('After trim of one index, Count = ' || va.count);
va.trim(2);
dbms_output.put_line('After trim of two indexes, Count = ' || va.count);
end loop;
end loop;
va.delete;
dbms_output.put_line('After delete of entire varray, Count = ' || va.count);
END;

Output:

Count = 4
Limit = 5
VARRAY ELEMENTS
va[1][1] = a


269

va[1][2] = b
va[1][3] = c
va[1][4] = d
va[2][1] = e
va[2][2] = f
va[2][3] = g
va[2][4] = h
va[3][1] = i
va[3][2] = j
va[3][3] = k
va[3][4] = l
va[4][1] = m
va[4][2] = n
va[4][3] = o
va[4][4] = p
First index = 1
Last index = 4
Next index = 3
Previous index = 2
Index 2 exists
VARRAY ELEMENTS
va[1][1] = a
va[1][2] = b
va[1][3] = c
va[1][4] = d
va[1][5] = q
va[2][1] = e
va[2][2] = f
va[2][3] = g
va[2][4] = h
va[2][5] = r
va[3][1] = i
va[3][2] = j
va[3][3] = k


270

va[3][4] = l
va[3][5] = s
va[4][1] = m
va[4][2] = n
va[4][3] = o
va[4][4] = p
va[4][5] = t
va[5][1] = u
va[5][2] = v
va[5][3] = w
va[5][4] = x
va[5][5] = y
After trim of two indexes, Count = 2
VARRAY ELEMENTS
va[1][1] = a
va[1][2] = b
va[2][1] = e
va[2][2] = f
After delete of entire varray, Count = 0

Ex2:
DECLARE

type t2 is table of t1;
nt t2 := t2();
c number := 65;
v number := 1;
flag boolean;
BEGIN

nt.extend(4);
if nt.limit is null then
dbms_output.put_line('No limit to Nested Tables');
else
dbms_output.put_line('Limit = ' || nt.limit);


271

end if;
for j in 1..nt.count loop
nt(i)(j) := chr(c);
c := c + 1;
if c = 91 then
c := 97;
end if;
end loop;
end loop;
dbms_output.put_line('nt[' || i || '][' || j || '] = ' || nt(i)(j));
end loop;
end loop;
dbms_output.put_line('First index = ' || nt.first);
dbms_output.put_line('Last index = ' || nt.last);
dbms_output.put_line('Next index = ' || nt.next(2));
dbms_output.put_line('Previous index = ' || nt.prior(3));
if flag = true then
else
end if;
nt.extend(2);
nt(1)(5) := 'Q';
nt(1)(6) := 'R';
nt(2)(5) := 'S';
nt(2)(6) := 'T';
nt(3)(5) := 'U';
nt(3)(6) := 'V';
nt(4)(5) := 'W';
nt(4)(6) := 'X';


272

nt(5)(1) := 'Y';
nt(5)(2) := 'Z';
nt(5)(3) := 'a';
nt(5)(4) := 'b';
nt(5)(5) := 'c';
nt(5)(6) := 'd';
nt(6)(1) := 'e';
nt(6)(2) := 'f';
nt(6)(3) := 'g';
nt(6)(4) := 'h';
nt(6)(5) := 'i';
nt(6)(6) := 'j';
dbms_output.put_line('After extend of one index, Count = ' || nt.count);
end loop;
end loop;
nt.trim;
dbms_output.put_line('After trim of one indexe, Count = ' || nt.count);
nt.trim(2);
dbms_output.put_line('After trim of two indexes, Count = ' || nt.count);
end loop;
end loop;
nt.delete(2);
dbms_output.put_line('After delete of second index, Count = ' || nt.count);
loop
exit when v = 4;
for j in 1..nt.count+1 loop


273

dbms_output.put_line('nt[' || v || '][' || j || '] = ' || nt(v)(j));
end loop;
v := v + 1;
if v= 2 then
v := 3;
end if;
end loop;
nt.delete;
dbms_output.put_line('After delete of entire nested table, Count = ' ||
nt.count);
END;

Output:
Count = 4
No limit to Nested Tables
nt[1][1] = A
nt[1][2] = B
nt[1][3] = C
nt[1][4] = D
nt[2][1] = E
nt[2][2] = F
nt[2][3] = G
nt[2][4] = H
nt[3][1] = I
nt[3][2] = J
nt[3][3] = K
nt[3][4] = L
nt[4][1] = M
nt[4][2] = N
nt[4][3] = O
nt[4][4] = P
First index = 1
Last index = 4


274

Next index = 3
Previous index = 2
Index 2 exists
nt[1][1] = A
nt[1][2] = B
nt[1][3] = C
nt[1][4] = D
nt[1][5] = Q
nt[1][6] = R
nt[2][1] = E
nt[2][2] = F
nt[2][3] = G
nt[2][4] = H
nt[2][5] = S
nt[2][6] = T
nt[3][1] = I
nt[3][2] = J
nt[3][3] = K
nt[3][4] = L
nt[3][5] = U
nt[3][6] = V
nt[4][1] = M
nt[4][2] = N
nt[4][3] = O
nt[4][4] = P
nt[4][5] = W
nt[4][6] = X
nt[5][1] = Y
nt[5][2] = Z
nt[5][3] = a
nt[5][4] = b
nt[5][5] = c
nt[5][6] = d


275

nt[6][1] = e
nt[6][2] = f
nt[6][3] = g
nt[6][4] = h
nt[6][5] = i
nt[6][6] = j
After trim of one indexe, Count = 5
After trim of two indexes, Count = 3
nt[1][1] = A
nt[1][2] = B
nt[1][3] = C
nt[2][1] = E
nt[2][2] = F
nt[2][3] = G
nt[3][1] = I
nt[3][2] = J
nt[3][3] = K
After delete of second index, Count = 2
nt[1][1] = A
nt[1][2] = B
nt[1][3] = C
nt[3][1] = I
nt[3][2] = J
nt[3][3] = K
After delete of entire nested table, Count = 0

Ex3:
DECLARE

type t2 is table of t1 index by binary_integer;
ibt t2;
flag boolean;
BEGIN



276

if ibt.limit is null then
dbms_output.put_line('No limit to Index-by Tables');
else
dbms_output.put_line('Limit = ' || ibt.limit);
end if;
ibt(1)(1) := 'a';
ibt(4)(5) := 'b';
ibt(5)(1) := 'c';
ibt(6)(2) := 'd';
ibt(8)(3) := 'e';
ibt(3)(4) := 'f';
dbms_output.put_line('INDEX-BY TABLE ELEMENTS');
dbms_output.put_line('ibt([1][1] = ' || ibt(1)(1));
dbms_output.put_line('First Index = ' || ibt.first);
dbms_output.put_line('Last Index = ' || ibt.last);
dbms_output.put_line('Next Index = ' || ibt.next(3));
dbms_output.put_line('Prior Index = ' || ibt.prior(8));
ibt(1)(2) := 'g';
ibt(1)(3) := 'h';
ibt(1)(4) := 'i';
ibt(1)(5) := 'k';
ibt(1)(6) := 'l';
ibt(1)(7) := 'm';
ibt(1)(8) := 'n';
for i in 1..8 loop
dbms_output.put_line('ibt[1][' || i || '] = ' || ibt(1)(i));
end loop;


277

if flag = true then
else
end if;
ibt.delete(1);
dbms_output.put_line('After delete of first index, Count = ' || ibt.count);
ibt.delete(4);
dbms_output.put_line('After delete of fourth index, Count = ' || ibt.count);
ibt.delete;
dbms_output.put_line('After delete of entire index-by table, Count = ' ||
ibt.count);
END;

Output:
Count = 0
No limit to Index-by Tables
INDEX-BY TABLE ELEMENTS
ibt([1][1] = a
ibt([4][5] = b
ibt([5][1] = c
ibt([6][2] = d
ibt([8][3] = e
ibt([3][4] = f
First Index = 1
Last Index = 8


278

Next Index = 4
Prior Index = 6
Count = 6
ibt[1][1] = a
ibt[1][2] = g
ibt[1][3] = h
ibt[1][4] = i
ibt[1][5] = k
ibt[1][6] = l
ibt[1][7] = m
ibt[1][8] = n
ibt([4][5] = b
ibt([5][1] = c
ibt([6][2] = d
ibt([8][3] = e
ibt([3][4] = f
Index 3 exists
After delete of fourth index, Count = 4
ibt([5][1] = c
ibt([6][2] = d
ibt([8][3] = e
ibt([3][4] = f
After delete of entire index-by table, Count = 0

Ex4:
DECLARE

type t2 is table of t1 index by binary_integer;
type t3 is table of t2;
nt t3 := t3();
c number := 65;
BEGIN

nt.extend(2);


279

for k in 1..nt.count loop
nt(i)(j)(k) := chr(c);
c := c + 1;
end loop;
end loop;
end loop;
for k in 1..nt.count loop
dbms_output.put_line('nt[' || i || '][' || j || '][' || k || '] = ' ||
nt(i)(j)(k));
end loop;
end loop;
end loop;
END;

Output:
Count = 2
nt[1][1][1] = A
nt[1][1][2] = B
nt[1][2][1] = C
nt[1][2][2] = D
nt[2][1][1] = E
nt[2][1][2] = F
nt[2][2][1] = G
nt[2][2][2] = H

OBJECTS USED IN THE EXAMPLES



280

SNO SNAME SMARKS
---------- -------------- ----------
1 saketh 100
2 srinu 200
3 divya 300
4 manogni 400

SQL> create or replace type addr as object(hno number(2),city
varchar(10));/

SQL> select * from employ;

ENAME JOB ADDRESS(HNO, CITY)
---------- ---------- -----------------------------
Ranjit clerk ADDR(11, 'hyd')
Satish manager ADDR(22, 'bang')
Srinu engineer ADDR(33, 'kochi')


281

ERROR HANDLING

PL/SQL implements error handling with exceptions and exception handlers. Exceptions
can be associated with oracle errors or with your own user-defined errors. By using
exceptions and exception handlers, you can make your PL/SQL programs robust and able
to deal with both unexpected and expected errors during execution.

ERROR TYPES
 Compile-time errors
 Runtime errors

Errors that occur during the compilation phase are detected by the PL/SQL engine and
reported back to the user, we have to correct them.

Runtime errors are detected by the PL/SQL runtime engine which can programmatically
raise and caught by exception handlers.
Exceptions are designed for run-time error handling, rather than compile-time error
handling.

HANDLING EXCEPTIONS


282

When exception is raised, control passes to the exception section of the block. The
exception section consists of handlers for some or all of the exceptions. An exception
handler contains the code that is executed when the error associated with the exception
occurs, and the exception is raised.

Syntax:
EXCEPTION

When exception_name then
Sequence_of_statements;
When exception_name then
When others then
END;

EXCEPTION TYPES

 Predefined exceptions

 User-defined exceptions

PREDEFINED EXCEPTIONS

Oracle has predefined several exceptions that corresponds to the most common oracle
errors. Like the predefined types, the identifiers of these exceptions are defined in the
STANDARD package. Because of this, they are already available to the program, it is not
necessary to declare them in the declarative secion.

Ex1:
DECLARE

a number;
b varchar(2);
v_marks number;
va t := t('a','b');
va1 t;
BEGIN


283

-- NO_DATA_FOUND
BEGIN

select smarks into v_marks from student where sno = 50;
EXCEPTION

when no_data_found then
dbms_output.put_line('Invalid student number');
END;
-- CURSOR_ALREADY_OPEN
BEGIN

open c;
open c;
EXCEPTION

when cursor_already_open then
dbms_output.put_line('Cursor is already opened');
END;

-- INVALID_CURSOR
BEGIN

close c;
open c;
close c;
close c;
EXCEPTION

when invalid_cursor then
dbms_output.put_line('Cursor is already closed');
END;
-- TOO_MANY_ROWS
BEGIN

select smarks into v_marks from student where sno > 1;
EXCEPTION

when too_many_rows then
dbms_output.put_line('Too many values are coming to marks
variable');
END;
-- ZERO_DIVIDE
BEGIN

a := 5/0;
EXCEPTION

when zero_divide then


284

dbms_output.put_line('Divided by zero - invalid operation');
END;
-- VALUE_ERROR
BEGIN

b := 'saketh';
EXCEPTION

when value_error then
dbms_output.put_line('Invalid string length');
END;
-- INVALID_NUMBER
BEGIN

insert into student values('a','srinu',100);
EXCEPTION

when invalid_number then
dbms_output.put_line('Invalid number');
END;

-- SUBSCRIPT_OUTSIDE_LIMIT
BEGIN

va(4) := 'c';
EXCEPTION

when subscript_outside_limit then
dbms_output.put_line('Index is greater than the limit');
END;
-- SUBSCRIPT_BEYOND_COUNT
BEGIN

va(3) := 'c';
EXCEPTION

when subscript_beyond_count then
dbms_output.put_line('Index is greater than the count');
END;
-- COLLECTION_IS_NULL
BEGIN

va1(1) := 'a';
EXCEPTION

when collection_is_null then
dbms_output.put_line('Collection is empty');
END;

--
END;


285

Output:
Invalid student number
Cursor is already opened
Cursor is already closed
Too many values are coming to marks variable
Divided by zero - invalid operation
Invalid string length
Invalid number
Index is greater than the limit
Index is greater than the count
Collection is empty

Ex2:
DECLARE

c number;
BEGIN

c := 5/0;
EXCEPTION

dbms_output.put_line('Invalid Operation');
when others then
dbms_output.put_line('From OTHERS handler: Invalid
Operation');
END;

Output:
Invalid Operation

USER-DEFINED EXCEPTIONS

A user-defined exception is an error that is defined by the programmer. User-defined
exceptions are declared in the declarative secion of a PL/SQL block. Just like variables,
exeptions have a type EXCEPTION and scope.


286

RAISING EXCEPTIONS

User-defined exceptions are raised explicitly via the RAISE statement.

Ex:
DECLARE

e exception;
BEGIN

raise e;
EXCEPTION

when e then
dbms_output.put_line('e is raised');
END;

Output:
e is raised
BULIT-IN ERROR FUNCTIONS

SQLCODE AND SQLERRM

 SQLCODE returns the current error code, and SQLERRM returns the current error
message text;

 For user-defined exception SQLCODE returns 1 and SQLERRM returns “user-deifned
exception”.
 SQLERRM wiil take only negative value except 100. If any positive value other than
100 returns non-oracle exception.

Ex1:
DECLARE

e exception;
v_dname varchar(10);
BEGIN
-- USER-DEFINED EXCEPTION
BEGIN

raise e;
EXCEPTION

when e then
dbms_output.put_line(SQLCODE || ' ' || SQLERRM);


287

END;

-- PREDEFINED EXCEPTION
BEGIN

select dname into v_dname from dept where deptno = 50;
EXCEPTION

when no_data_found then
dbms_output.put_line(SQLCODE || ' ' || SQLERRM);
END;
END;

Output:
1 User-Defined Exception
100 ORA-01403: no data found

Ex2:
BEGIN

dbms_output.put_line(SQLERRM(100));
dbms_output.put_line(SQLERRM(-100));
END;

Output:
ORA-01403: no data found
ORA-0000: normal, successful completion
User-Defined Exception
ORA-00100: no data found
ORA-00500: Message 500 not found; product=RDBMS; facility=ORA
-200: non-ORACLE exception
ORA-00900: invalid SQL statement

DBMS_UTILITY.FORMAT_ERROR_STACK


288

 The built-in function, like SQLERRM, returns the message associated with the current
error.

 It differs from SQLERRM in two ways:
 Its length is not restricted; it will return the full error message string.
 You can not pass an error code number to this function; it cannot be used to return
the message for a random error code.

Ex:
DECLARE

v number := 'ab';
BEGIN

null;
EXCEPTION

when others then
dbms_output.put_line(dbms_utility.format_error_stack);
END;

Output:
declare
*
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: character to number conversion
error
ORA-06512: at line 2

DBMS_UTILITY.FORMAT_CALL_STACK

This function returns a formatted string showing the execution call stack inside your
PL/SQL application. Its usefulness is not restricted to error management; you will also find
its handy for tracing the exectution of your code. You may not use this function in
exception block.

Ex:
BEGIN

dbms_output.put_line(dbms_utility.format_call_stack);
END;


289

Output:
----- PL/SQL Call Stack -----
Object_handle line_number object_name
69760478 2 anonymous block

DBMS_UTILITY.FORMAT_ERROR_BACKTRACE

It displays the execution stack at the point where an exception was raised. Thus , you can
call this function with an exception section at the top level of your stack and still find out
where the error was raised deep within the call stack.

Ex:
CREATE OR REPLACE PROCEDURE P1 IS
BEGIN

dbms_output.put_line('from procedure 1');
raise value_error;
END P1;
BEGIN

p1;
END P2;

BEGIN

p2;
EXCEPTION

when others then
dbms_output.put_line(dbms_utility.format_error_backtrace);
END P3;

Output:
SQL> exec p3

from procedure 3
from procedure 2
from procedure 1


290

ORA-06512: at "SAKETH.P1", line 4

EXCEPTION_INIT PRAGMA

Using this you can associate a named exception with a particular oracle error. This gives
you the ability to trap this error specifically, rather than via an OTHERS handler.

Syntax:
PRAGMA EXCEPTION_INIT(exception_name, oracle_error_number);
Ex:
DECLARE

e exception;
pragma exception_init(e,-1476);
c number;
BEGIN

c := 5/0;
EXCEPTION

when e then
dbms_output.put_line('Invalid Operation');
END;

Output:
Invalid Operation

RAISE_APPLICATION_ERROR

You can use this built-in function to create your own error messages, which can be more
descriptive than named exceptions.

Syntax:
RAISE_APPLICATION_ERROR(error_number, error_message,, [keep_errors_flag]);


291

The Boolean parameter keep_errors_flag is optional. If it is TRUE, the new error is added
to the list of errors already raised. If it is FALSE, which is default, the new error will
replace the current list of errors.

Ex:
DECLARE

c number;
BEGIN

c := 5/0;

EXCEPTION

raise_application_error(-20222,'Invalid Operation');
END;

Output:
DECLARE

*
ERROR at line 1:
ORA-20222: Invalid Operation

EXCEPTION PROPAGATION

Exceptions can occur in the declarative, the executable, or the exception section of a
PL/SQL block.

EXCEPTION RAISED IN THE EXECUATABLE SECTION

Exceptions raised in execuatable section can be handled in current block or outer block.

Ex1:
DECLARE

e exception;
BEGIN
BEGIN

raise e;
END;


292

EXCEPTION

when e then
END;

Output:
e is raised

Ex2:
DECLARE

e exception;
BEGIN
BEGIN

raise e;
END;
END;

Output:
ERROR at line 1:
ORA-06510: PL/SQL: unhandled user-defined exception

EXCEPTION RAISED IN THE DECLARATIVE SECTION

Exceptions raised in the declarative secion must be handled in the outer block.

Ex1:
DECLARE

c number(3) := 'abcd';
BEGIN

dbms_output.put_line('Hello');
EXCEPTION

when others then
END;

Output:
ERROR at line 1:


293

ORA-06502: PL/SQL: numeric or value error: character to number conversion
error

Ex2:
BEGIN
DECLARE

c number(3) := 'abcd';
BEGIN

dbms_output.put_line('Hello');
EXCEPTION

when others then
END;
EXCEPTION

when others then
dbms_output.put_line('From outer block: Invalid string length');
END;

Output:
From outer block: Invalid string length

EXCEPTION RAISED IN THE EXCEPTION SECTION

Exceptions raised in the declarative secion must be handled in the outer block.

Ex1:
DECLARE

e1 exception;
e2 exception;
BEGIN

raise e1;
EXCEPTION

when e1 then
dbms_output.put_line('e1 is raised');
raise e2;
when e2 then


294

END;

Output:
e1 is raised
DECLARE
*
ERROR at line 1:

Ex2:
DECLARE

e1 exception;
e2 exception;
BEGIN
BEGIN

raise e1;
EXCEPTION

when e1 then
raise e2;
when e2 then
END;
EXCEPTION

when e2 then
dbms_output.put_line('From outer block: e2 is raised');
END;

Output:
e1 is raised
From outer block: e2 is raised

Ex3:
DECLARE

e exception;


295

BEGIN

raise e;
EXCEPTION

when e then
raise e;
END;

Output:
e is raised
DECLARE
*
ERROR at line 1:

RESTRICTIONS

You can not pass exception as an argument to a subprogram.


296

DATABASE TRIGGERS

Triggers are similar to procedures or functions in that they are named PL/SQL blocks with
declarative, executable, and exception handling sections. A trigger is executed implicitly
whenever the triggering event happens. The act of executing a trigger is known as firing
the trigger.

RESTRICTIONS ON TRIGGERES

 Like packages, triggers must be stored as stand-alone objects in the database and
cannot be local to a block or package.
 A trigger does not accept arguments.

USE OF TRIGGERS

 Maintaining complex integrity constraints not possible through declarative
constraints enable at table creation.


297

 Auditing information in a table by recording the changes made and who made
them.
 Automatically signaling other programs that action needs to take place when
chages are made to a table.
 Perform validation on changes being made to tables.
 Automate maintenance of the database.

TYPES OF TRIGGERS

 DML Triggers
 Instead of Triggers
 DDL Triggers
 System Triggers
 Suspend Triggers

CATEGORIES

Timing -- Before or After
Level -- Row or Statement

Row level trigger fires once for each row affected by the triggering statement. Row level
trigger is identified by the FOR EACH ROW clause.

Statement level trigger fires once either before or after the statement.

DML TRIGGER SYNTAX

Create or replace trigger <trigger_name>
{Before | after} {insert or update or delete} on <table_name>
[For each row]
[When (…)]
[Declare]


298

-- declaration
Begin
-- trigger body
[Exception]
End <trigger_name>;

DML TRIGGERS

A DML trigger is fired on an INSERT, UPDATE, or DELETE operation on a database table. It can
be fired either before or after the statement executes, and can be fired once per affected
row, or once per statement.

The combination of these factors determines the types of the triggers. These are a total of
12 possible types (3 statements * 2 timing * 2 levels).

STATEMENT LEVEL

Statement level trigger fires only once.
Ex:

SQL> create table statement_level(count varchar(50));

CREATE OR REPLACE TRIGGER STATEMENT_LEVEL_TRIGGER

after update on student
BEGIN

insert into statement_level values('Statement level fired');
END STATEMENT_LEVEL_TRIGGER;

Output:

SQL> update student set smarks=500;

3 rows updated.

SQL> select * from statement_level;


299

COUNT
----------------------------
Statement level fired

ROW LEVEL

Row level trigger fires once for each row affected by the triggering statement.

Ex:

SQL> create table row_level(count varchar(50));

CREATE OR REPLACE TRIGGER ROW_LEVEL_TRIGGER

after update on student
BEGIN

insert into row_level values('Row level fired');
END ROW_LEVEL_TRIGGER;

Output:

SQL> update student set smarks=500;

3 rows updated.

SQL> select * from statement_level;

COUNT
----------------------------
Row level fired
Row level fired
Row level fired

ORDER OF DML TRIGGER FIRING

 Before statement level
 Before row level


300

 After row level
 After statement level

Ex:
Suppose we have a follwing table.


NO NAME MARKS
----- ------- ----------
1 a 100
2 b 200
3 c 300
4 d 400

SQL> create table firing_order(order varchar(50));

CREATE OR REPLACE TRIGGER BEFORE_STATEMENT

before insert on student
BEGIN

insert into firing_order values('Before Statement Level');
END BEFORE_STATEMENT;

CREATE OR REPLACE TRIGGER BEFORE_ROW

before insert on student
for each row
BEGIN

insert into firing_order values('Before Row Level');
END BEFORE_ROW;

CREATE OR REPLACE TRIGGER AFTER_STATEMENT

after insert on student
BEGIN

insert into firing_order values('After Statement Level');
END AFTER_STATEMENT;

CREATE OR REPLACE TRIGGER AFTER_ROW



301

for each row
BEGIN

insert into firing_order values('After Row Level');
END AFTER_ROW;

Output:
SQL> select * from firing_order;

no rows selected

SQL> insert into student values(5,'e',500);

1 row created.

SQL> select * from firing_order;

ORDER
--------------------------------------------------
Before Statement Level
Before Row Level
After Row Level
After Statement Level


NO NAME MARKS
---- -------- ----------
1 a 100
2 b 200
3 c 300
4 d 400
5 e 500

CORRELATION IDENTIFIERS IN ROW-LEVEL TRIGGERS


302

Inside the trigger, you can access the data in the row that is currently being processed.
This is accomplished through two correlation identifiers - :old and :new.

A correlation identifier is a special kind of PL/SQL bind variable. The colon in front of each
indicates that they are bind variables, in the sense of host variables used in embedded
PL/SQL, and indicates that they are not regular PL/SQL variables. The PL/SQL compiler will
treat them as records of type

Triggering_table%ROWTYPE.

Although syntactically they are treated as records, in reality they are not. :old and :new
are also known as pseudorecords, for this reason.

TRIGGERING STATEMENT :OLD :NEW
-------------------------------------- ---------------------------- -----------------------------------------------

INSERT all fields are NULL. values that will be inserted
When the statement is completed.
UPDATE original values for new values that will be updated
the row before the when the statement is completed.
update.
DELETE original values before all fields are NULL.
the row is deleted.

Ex:
SQL> create table marks(no number(2) old_marks number(3),new_marks
number(3));

CREATE OR REPLACE TRIGGER OLD_NEW

before insert or update or delete on student
for each row
BEGIN

insert into marks values(:old.no,:old.marks,:new.marks);
END OLD_NEW;

Output:


303

NO NAME MARKS
----- ------- ----------
1 a 100
2 b 200
3 c 300
4 d 400
5 e 500

SQL> select * from marks;

no rows selected

SQL> insert into student values(6,'f',600);

1 row created.


NO NAME MARKS
---- -------- ----------
1 a 100
2 b 200
3 c 300
4 d 400
5 e 500
6 f 600


NO OLD_MARKS NEW_MARKS
---- --------------- ---------------
600

SQL> update student set marks=555 where no=5;


304

1 row updated.


NO NAME MARKS
----- ------- ----------
1 a 100
2 b 200
3 c 300
4 d 400
5 e 555
6 f 600


------ ---------------- ---------------
600
5 500 555


1 row deleted.


NO NAME MARKS
---- -------- ----------
1 a 100
3 c 300
4 d 400
5 e 555
6 f 600


305


----- -------------- ----------------
600
5 500 555
2 200

REFERENCING CLAUSE

If desired, you can use the REFERENCING clause to specify a different name for :old ane
:new. This clause is found after the triggering event, before the WHEN clause.

Syntax:
REFERENCING [old as old_name] [new as new_name]
Ex:
CREATE OR REPLACE TRIGGER REFERENCE_TRIGGER

referencing old as old_student new as new_student
for each row
BEGIN

insert into marks
values(:old_student.no,:old_student.marks,:new_student.marks);
END REFERENCE_TRIGGER;

WHEN CLAUSE

WHEN clause is valid for row-level triggers only. If present, the trigger body will be
executed only for those rows that meet the condition specified by the WHEN clause.

Syntax:
WHEN trigger_condition;

Where trigger_condition is a Boolean expression. It will be evaluated for each row. The
:new and :old records can be referenced inside trigger_condition as well, but like
REFERENCING, the colon is not used there. The colon is only valid in the trigger body.


306

Ex:
CREATE OR REPLACE TRIGGER WHEN_TRIGGER

referencing old as old_student new as new_student
for each row
when (new_student.marks > 500)
BEGIN

insert into marks
values(:old_student.no,:old_student.marks,:new_student.marks);
END WHEN_TRIGGER;

TRIGGER PREDICATES

There are three Boolean functions that you can use to determine what the operation is.
The predicates are

 INSERTING
 UPDATING
 DELETING

Ex:

SQL> create table predicates(operation varchar(20));

CREATE OR REPLACE TRIGGER PREDICATE_TRIGGER

BEGIN

if inserting then
insert into predicates values('Insert');
elsif updating then
insert into predicates values('Update');
elsif deleting then
insert into predicates values('Delete');
end if;
END PREDICATE_TRIGGER;

Output:
SQL> delete student where no=1;


307

1 row deleted.

SQL> select * from predicates;

MSG
---------------
Delete

SQL> insert into student values(7,'g',700);

1 row created.


MSG
---------------
Delete
Insert

SQL> update student set marks = 777 where no=7;

1 row updated.


MSG
---------------
Delete
Insert
Update

INSTEAD-OF TRIGGERS


308

Instead-of triggers fire instead of a DML operation. Also, instead-of triggers can be defined
only on views. Instead-of triggers are used in two cases:

 To allow a view that would otherwise not be modifiable to be modified.
 To modify the columns of a nested table column in a view.

Ex:
SQL> create view emp_dept as select empno,ename,job,dname,loc,sal,e.deptno from
emp e, dept d where e.deptno = d.deptno;

CREATE OR REPLACE TRIGGER INSTEAD_OF_TRIGGER

instead of insert on emp_dept
BEGIN

insert into dept1 values(50,'rd','bang');
insert into
emp1(empno,ename,job,sal,deptno)values(2222,'saketh','doctor',8000,50);
END INSTEAD_OF_TRIGGER;

Output:

SQL> insert into emp_dept values(2222,'saketh','doctor',8000,'rd','bang',50);
SQL> select * from emp_dept;

EMPNO ENAME JOB SAL DNAME LOC DEPTNO
---------- ---------- ------------ ----------- ------------- ------------- ----------
7369 SMITH CLERK 800 RESEARCH DALLAS 20
7499 ALLEN SALESMAN 1600 SALES CHICAGO 30
7521 WARD SALESMAN 1250 SALES CHICAGO 30
7566 JONES MANAGER 2975 RESEARCH DALLAS 20
7654 MARTIN SALESMAN 1250 SALES CHICAGO 30
7698 BLAKE MANAGER 2850 SALES CHICAGO 30
7782 CLARK MANAGER 2450 ACCOUNTING NEW YORK 10
7788 SCOTT ANALYST 3000 RESEARCH DALLAS 20
7839 KING PRESIDENT 5000 ACCOUNTING NEW YORK 10
7844 TURNER SALESMAN 1500 SALES CHICAGO 30
7876 ADAMS CLERK 1100 RESEARCH DALLAS 20
7900 JAMES CLERK 950 SALES CHICAGO 30


309

7902 FORD ANALYST 3000 RESEARCH DALLAS 20
7934 MILLER CLERK 1300 ACCOUNTING NEW YORK 10
2222 saketh doctor 8000 rd bang 50


DEPTNO DNAME LOC
---------- ---------------- -----------
20 RESEARCH DALLAS
30 SALES CHICAGO
50 rd bang

SQL> select * from emp;

---------- ---------- --------------- -------- -------------- --------- --------- ----------
7369 SMITH CLERK 7902 1 7-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
2222 saketh doctor 8000 50


310

DDL TRIGGERS

Oracle allows you to define triggers that will fire when Data Definition Language
statements are executed.

Syntax:

{Before | after} {DDL event} on {database | schema}
[When (…)]
[Declare]
-- declaration
Begin
-- trigger body
[Exception]
End <trigger_name>;

Ex:

SQL> create table my_objects(obj_name varchar(10),obj_type varchar(10),obj_owner
varchar(10),obj_time date);

CREATE OR REPLACE TRIGGER CREATE_TRIGGER

after create on database
BEGIN

insert into my_objects values(sys.dictionary_obj_name,sys.dictionary_obj_type,
sys.dictionary_obj_owner, sysdate);
END CREATE_TRIGGER;

Output:

SQL> select * from my_objects;

no rows selected


311

SQL> create table stud1(no number(2));


OBJ_NAME OBJ_TYPE OBJ_OWNER OBJ_TIME
------------- -------------- -------------- ------------
STUD1 TABLE SYS 21-JUL-07

SQL> create sequence ss;

SQL> create view stud_view as select * from stud1;


OBJ_NAME OBJ_TYPE OBJ_OWNER OBJ_TIME
-------------- ------------- ---------------- -------------
STUD1 TABLE SYS 21-JUL-07
SS SEQUENCE SYS 21-JUL-07
STUD_VIEW VIEW SYS 21-JUL-07

WHEN CLAUSE

If WHEN present, the trigger body will be executed only for those that meet the condition
specified by the WHEN clause.

Ex:
CREATE OR REPLACE TRIGGER CREATE_TRIGGER

after create on database
when (sys.dictionary_obj_type = ‘TABLE’)
BEGIN

insert into my_objects values(sys.dictionary_obj_name,sys.dictionary_obj_type,
sys.dictionary_obj_owner, sysdate);
END CREATE_TRIGGER;


312

SYSTEM TRIGGERS

System triggers will fire whenever database-wide event occurs. The following are the
database event triggers. To create system trigger you need ADMINISTER DATABASE TRIGGER
privilege.

 STARTUP
 SHUTDOWN
 LOGON
 LOGOFF
 SERVERERROR

Syntax:

{Before | after} {Database event} on {database | schema}
[When (…)]
[Declare]
-- declaration section
Begin
-- trigger body
[Exception]
End <trigger_name>;

Ex:

SQL> create table user_logs(u_name varchar(10),log_time timestamp);

CREATE OR REPLACE TRIGGER AFTER_LOGON

after logon on database
BEGIN

insert into user_logs values(user,current_timestamp);
END AFTER_LOGON;

Output:


313

SQL> select * from user_logs;

no rows selected


U_NAME LOG_TIME
---------- ------------------------------------------------
SAKETH 22-JUL-07 12.07.13.140000 AM

SQL> conn system/oracle

U_NAME LOG_TIME
---------- ------------------------------------------------
SAKETH 22-JUL-07 12.07.13.140000 AM
SYSTEM 22-JUL-07 12.07.34.218000 AM

SQL> conn scott/tiger

U_NAME LOG_TIME
---------- -----------------------------------------------
SAKETH 22-JUL-07 12.07.13.140000 AM
SYSTEM 22-JUL-07 12.07.34.218000 AM
SCOTT 22-JUL-07 12.08.43.093000 AM

SERVERERROR

The SERVERERROR event can be used to track errors that occur in the database. The error
code is available inside the trigger through the SERVER_ERROR attribute function.
Ex:


314

SQL> create table my_errors(error_msg varchar(200));

CREATE OR REPLACE TRIGGER SERVER_ERROR_TRIGGER

after servererror on database
BEGIN

insert into my_errors values(dbms_utility.format_error_stack);
END SERVER_ERROR_TRIGGER;

Output:

SQL> create table ss (no));
create table ss (no))
*
ERROR at line 1:
ORA-00922: missing or invalid option

SQL> select * from my_errors;
ERROR_MSG
-------------------------------------------------------------

SQL> insert into student values(1,2,3);
insert into student values(1,2,3)
*
ERROR at line 1:

SQL> select * from my_errors;

ERROR_MSG
-------------------------------------------------------------

SERVER_ERROR ATTRIBUTE FUNCTION


315

It takes a single number type of argument and returns the error at the position on the
error stack indicated by the argument. The position 1 is the top of the stack.

Ex:

CREATE OR REPLACE TRIGGER SERVER_ERROR_TRIGGER

after servererror on database
BEGIN

insert into my_errors values(server_error(1));
END SERVER_ERROR_TRIGGER;

SUSPEND TRIGGERS

This will fire whenever a statement is suspended. This might occur as the result of a
space issue such as exceeding an allocated tablepace quota. This functionality can be
used to address the problem and allow the operatin to continue.

Syntax:

after suspend on {database | schema}
[When (…)]
[Declare]
-- declaration section
Begin
-- trigger body
[Exception]
End <trigger_name>;

Ex:

SQL> create tablespace my_space datafile 'f:my_file.dbf' size 2m;
SQL> create table student(sno number(2),sname varchar(10)) tablespace my_space;

CREATE OR REPLACE TRIGGER SUSPEND_TRIGGER


316

after suspend on database
BEGIN

dbms_output.put_line(‘ No room to insert in your tablespace');
END SUSPEND_TRIGGER;

Output:

Insert more rows in student table then , you will get

No room to insert in your tablespace

AUTONOMOUS TRANSACTION

Prior to Oracle8i, there was no way in which some SQL operations within a transaction
could be committed independent of the rest of the operations. Oracle allows this,
however, through autonomous transactions. An autonomous transaction is a transaction
that is started within the context of another transaction, known as parent transaction, but
is independent of it. The autonomous transaction can be committed or rolled back
regardless ot the state of the parent transaction.

Ex:

CREATE OR REPLACE TRIGGER AUTONOMOUS_TRANSACTION_TRIGGER

DECLARE

pragma autonomous_transaction;
BEGIN

update student set marks = 555;
commit;
END AUTONOMOUS_TRANSACTION_TRIGGER;

Output:


NO NA MARKS
----- ----- -- ----------


317

1 a 111
2 b 222
3 c 300

SQL> insert into student values(4,'d',444);


NO NA MARKS
---- ------ -- ----------
1 a 555
2 b 555
3 c 555
4 d 444

RESTRICTIONS ON AUTONOMOUS TRANSACTION

 If an autonomous transaction attempts to access a resource held by the main
transaction, a deadlock can occur in you program.

 You cannot mark all programs in a package as autonomous with a single PRAGMA

declaration. You must indicate autonomous transactions explicity in each program.

 To exit without errors from an autonomous transaction program that has executed
at least one INSERT or UPDATE or DELETE, you must perform an explicit commit or
rollback.

 The COMMIT and ROLLBACK statements end the active autonomous transaction, but
they do not force the termination of the autonomous routine. You can have multiple
COMMIT and/or ROLLBACK statements inside your autonomous block.
 You can not rollback to a savepoint set in the main transaction.

 The TRANSACTIONS parameter in the oracle initialization file specifies the maximum
number of transactions allowed concurrently in a session. The default value is 75
for this, but you can increase the limit.

MUTATING TABLES


318

There are restrictions on the tables and columns that a trigger body may access. In order
to define these restrictions, it is necessary to understand mutating and constraining
tables.

A mutating table is table that is currentlty being modified by a DML statement and the
trigger event also DML statement. A mutating table error occurs when a row-level trigger
tries to examine or change a table that is already undergoing change.

A constraining table is a table that might need to be read from for a referential integrity
constraint.

Ex:

CREATE OR REPLACE TRIGGER MUTATING_TRIGGER

before delete on student
for each row

DECLARE

ct number;
BEGIN

select count(*) into ct from student where no = :old.no;
END MUTATING_TRIGGER;

Output:

delete student where no = 1
*
ERROR at line 1:
ORA-04091: table SCOTT.STUDENT is mutating, trigger/function may not see it
ORA-06512: at "SCOTT.T", line 4
ORA-04088: error during execution of trigger 'SCOTT.T'

HOW TO AVOID MUTATING TABLE ERROR ?

 By using autonomous transaction
 By using statement level trigger


319


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