PL/SQL Constants Variable | Declare PL/SQL Constants

You can declare PL/SQL constants along with the value and can not change them throughout the program block. The constants declaration functionality is available in almost all programming languages.

PL/SQL Constant Declaration Syntax

The general syntax for declaring a constant variable is:

Constant_name CONSTANT Datatype[Size] := Value; 

Explanation:

• Constant_name is a predefined name of the constant (similar to a variable name).
• CONSTANT is a reserved keyword.
• Data type is a valid PL/SQL data type.
• Size is an optional specification of data type. It holds maximum capacity value for the particular variable.
• Value must be assigned to a constant when it is declared. You can not assign or change it later.
• Each constant declaration is terminated by a semicolon.

Constant Example

In this example, we will store the employee number which is NOT NULL (compulsory), employee Name and employee department which is constant,
Example Code :

DECLARE
 eno number(5) NOT NULL := 2
 ename varchar2(15) := 'Branson Devs';
 edept CONSTANT varchar2(15) := 'Web Developer';
BEGIN
 dbms_output.put_line('Declared Value:');
 dbms_output.put_line(' Employee number: ' || eno || ' Employee Name: ' || ename);
 dbms_output.put_line('Constant Declared:');
 dbms_output.put_line(' Employee Department: ' || edept); 
END;
/

Backward slash '/' is indicated to execute the above PL/SQL Block Program.
Example Result :

Declared Value:
Employee number: 2 Employee Name: Branson Devs
Constant Declared:
Employee Department: Web Developer

PL/SQL procedure successfully operation.

Variable/Constant Declarations Example

In this example, we will store the pi which is constant real number, radius and area which are real number,
Example Code :

DECLARE
 pi CONSTANT REAL := 3.14159;
   radius REAL := 3;
   area REAL := (pi * radius**2);
BEGIN
 dbms_output.put_line(' PI: ' || pi || ' Radius: ' || radius);
 dbms_output.put_line(' Area: ' || area); 
END;
/

Example Result :

PI: 3.14159 Radius: 1
Area: 28.27431