Constant Syntax

The General Syntax to declare a constant is:

constant_name CONSTANT datatype := VALUE;

• constant_name is the name of the constant i.e. similar to a variable name.
• The word CONSTANT  is a reserved word and ensures that the value does not change.
• VALUE - It is a value which must be assigned to a constant when it is declared. You cannot assign a value later.

For example, to declare salary_increase, you can write code as follows:

DECLARE 

salary_increase CONSTANT number (3) := 10; 

You must assign a value to a constant at the time you declare it. If you do not assign a value to a constant while declaring it and try to assign a value in the execution section, you will get a error. If you execute the below Pl/SQL block you will get error.

DECLARE 

 salary_increase CONSTANT number(3); 

BEGIN 

 salary_increase := 100; 

 dbms_output.put_line (salary_increase); 

END;