PL/pgSQL – Constants

ByAdmin

In PostgreSQL’s PL/pgSQL language, you can create constants using the CONSTANT keyword. Constants are values that don’t change during the execution of a PL/pgSQL block and are typically used for storing values that you want to use without modification throughout your code. Constants can be of various data types, including numeric, text, or custom types.

Here’s the basic syntax for declaring constants in PL/pgSQL:

DECLARE constant_name CONSTANT data_type := value;

where

  • constant_name is the name you want to give to the constant.
  • data_type is the data type of the constant.
  • value is the initial value to the constant.

Here’s an example of declaring and using constants in PL/pgSQL:

DECLARE 
 pi CONSTANT numeric := 3.141592653589793; 
 author_name CONSTANT text := 'John Smith'; 
BEGIN 
 RAISE NOTICE 'The value of pi is %', pi; 
 RAISE NOTICE 'The author is %', author_name; 
END;

In this example:

  • We declare two constants: pi and author_name.
  • pi is a constant of type numeric with an initial value of the mathematical constant π (pi).
  • author_name is a constant of type text with an initial value of ‘John Smith’.

Inside the PL/pgSQL block, we use the RAISE NOTICE statement to print the values of these constants.

Constants are immutable within the scope of the PL/pgSQL block. You cannot change their values once they are assigned.

Constants can be used for storing values that you want to reuse multiple times within the block, improving code readability and maintainability.

Constants can be used in expressions, assignments, and conditional statements like any other variables or values.

Using constants in PL/pgSQL can make your code more self-explanatory and reduce the risk of accidental changes to important values.

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