Chapter -02 Declaring PL/SQL Variables - 01

Objectives

After completing this lesson,you should be able to do the following

• Recognize valid and invalid identifies.
• List the uses of variables.
• Declare and initialize variables.
• List and descible various data types.
• Indentify the benefits of using the %TYPE attribute.
• Declare,use and print bind variables. 

Use of Vaiables

Variables can be used for:

• Temporary storage of data
• Manipulation of stored values
• Reusability

Demo

DECLARE
v_fname  VARCHAR2(20);
v_deptno NUMBER(4);
BEGIN

        SELECT first_name,department_id INTO v_fname,v_deptno
        FROM employees
        WHERE employee_id = 100;

        DBMS_OUTPUT.PUT_LINE('The first_name is ' || v_fname);
        DBMS_OUTPUT.PUT_LINE('The department_no is ' || v_deptno);

END;
/

SQL> @variables.sql
The first_name is Steven
The department_no is 90

PL/SQL procedure successfully completed.

Requirements for Variable Names

A variable name:

• Must start with a letter
• Can include letters or numbers
• Can include special characters(such as $,_,and #)
• Must conatin no more than 30 characters
• Must not include reserverd words

Handing Variables in PL/SQL

Variables are:

• Declared and initialized in the declarative section
• Used and assigned new values in the executable section
• Passed as parameters to PL/SQL subprograms
• Used to hold the output of a PL/SQL subprogram

Declaring an Initializing PL/SQL Variables

• Syntax:

identifier [CONSTRANT] datetype [NOT NULL] [:= | DEFATULT expr];

• Examples:

DECLARE
    v_hiredate    DATE;
    v_deptno      NUMBER(2)    NOT NULL    := 10;
    v_location    VARCHAR2(13)             := 'Atlanta';
    v_comm        CONSTANT NUMBER          := 1400;

Demo 01

DECLARE
        v_myName        VARCHAR2(20);
BEGIN
        DBMS_OUTPUT.PUT_LINE('My name is :' || v_myName);
        v_myName := 'ArcerZhang';
        DBMS_OUTPUT.PUT_LINE('My name is :' || v_myName);
END;
/

Demo 02

DECLARE
        v_myName        VARCHAR2(20) := 'John';
BEGIN
        v_myName := 'Steven';
        DBMS_OUTPUT.PUT_LINE('My name is : ' || v_myName);
END;
/