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Variables can be used for:

1- Temporary storage of data.

2- Manipulation of stored data.

3- Reusability.

4- Ease of maintenance.

USE OF VARIABLES

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1- PL/SQL Variables :

- Scalar- Composite

- Reference

- LOB(large objects)2- Non-PL/SQL variables :

Bind and Host variables

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SYNTAX :identifier [constant] datatype [NOT NULL] [:= |

DEFAULT expression];

EXAMPLE :

DECLAREv_hiredate date;v_deptno number(2) not null :=10;v_location varchar2(13):=‘Atlants’; 

Declaring PL/SQL variables

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A bind variable is a variable that you declare in ahost environment. Bind variable can be used to passrun-time values, either number or character , into orout of one or more PL/SQL program.

Creating BIND VARIABLESTo declare bind variable in the ISQL*Plus

environment, use the command VARIABLE. Forexample, you declare a variable of type number andvarchar2 as follows :

VARIABLE return_code NUMBER

VARIABLE return_msg VARCHAR2

BIND VARIABLES

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To reference a bind variable in PL/SQL , you must prefixits name colon(:).

EXAMPLE :

Using Bind Variable

VARIABLE g_salary NUMBER

BEGINSELECT salaryINTO :g_salaryFROM employeesWHERE employee_id=178;

END;/

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► A Oracle-supplied packaged procedure

► An alternative for displaying data from a PL/SQL block

► Must be enabled in ISQL*Plus with: set serveroutput on

DBMS_OUTPUT.PUT_LINE

SET SERVEROUTPUT ONDEFINE p_annual_sal =60000

DECLARE

v_sal NUMBER(9,2) :=&p_annual_sal;BEGIN

v_sal:=v_sal/12;DBMS_OUTPUT.PUT_LINE(‘The monthly salary is’||TO_CHAR(V_sal)); 

END;/

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Identifiers are used to name PL/SQL program items and units ,which includes constant , variables , exceptions , cursor variable ,subprograms and packages.

Can contain up to 30 characters

Must begin with an alphabetic character

Can contain numerals , dollar sign , underscores , and number

sign.Cannot contain characters such as hyphens , slashes , and spaces.

Should not have the same name as a database table columnname.

Should not be reserved words

IDENTIFIERS

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► Prefix single-line comments with two dashes (--)

► Place multiple-line comments between the symbols

/* and */

COMMENTING CODE

EXAMPLE :-DECLARE…………….. 

v_sal NUMBER(9,2);BEGIN/* Compute the annual salary based on the monthly salary

input from the user*/v_sal := :g_monthly_sal*12;

END; -- This is the end of the block.

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Available in procedural statements

-- Single-row number-- Single-row character

-- Data type conversion

-- Date

-- TimestampNot available in procedural statements

-- DECODE

-- Group Functions

SQL Functions in PL/SQL

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■ LOGICAL

■ ARITHMETIC

■ CONCATENATION

■ PARENTHESES TO CONTROL ORDEROF OPERATIONS

■ EXPONENTIAL OPERATOR (**)

OPERATORS IN PL/SQL