Learn SQL Database Programming

Learning how to create and use functions

The syntax to create a function is quite similar to creating a stored procedure:

DELIMITER $$ CREATE FUNCTION functionname( parameter1, parameter2,… ) RETURNS datatype [NOT] DETERMINISTIC BEGIN -- put sql statements here END $$ DELIMITER ;

DELIMITER lets MySQL know that there may be lines in-between the delimiter statements that end in a semicolon. If you don't put DELIMITER around a function, you will get an error when MySQL hits the semicolon in your first SQL query, inside the stored procedure.

A function can be deterministic or non-deterministic. Deterministic always returns the same result for the same input parameters, whereas non-deterministic doesn't.

Let's walk through an example. You can ...