Constant - (PL/SQL Tutorial)

In PL/SQL, a constant is an identifier that is assigned a value that cannot be changed during program execution. It is a kind of variable that behaves like a read-only variable. Constants are useful for storing values that are used repeatedly in a program.

Syntax

The syntax for defining a constant in PL/SQL is as follows:

CONSTANT constant_name constant_data_type := constant_value;

Here, constant_name is the name of the constant, constant_data_type is the data type of the constant, and constant_value is the value assigned to the constant.

Example

Here is an example of defining a constant in PL/SQL:

DECLARE
   pi CONSTANT NUMBER := 3.14159;
   message CONSTANT VARCHAR2(20) := 'Hello, World!';
BEGIN
   DBMS_OUTPUT.PUT_LINE(pi);
   DBMS_OUTPUT.PUT_LINE(message);
END;

Output

The output of the above program will be:

3.14159
Hello, World!

Explanation

In the above example, we have defined two constants, pi and message. pi has a value of 3.14159 and is of data type NUMBER, and message has a value of Hello, World! and is of data type VARCHAR2. We have then used the DBMS_OUTPUT.PUT_LINE procedure to display the values of the constants.

Use

Constants are used to store values that do not change during program execution. They are useful for storing values that are used repeatedly in a program, as they save memory and make programs easier to read and maintain.

Important Points

• A constant is an identifier that is assigned a value that cannot be changed during program execution.
• Constants are useful for storing values that are used repeatedly in a program.
• The syntax for defining a constant is CONSTANT constant_name constant_data_type := constant_value;.

Summary

In summary, a constant in PL/SQL is a read-only variable that is assigned a value that cannot be changed during program execution. Constants are useful for storing values that are used repeatedly in a program, as they save memory and make programs easier to read and maintain.