Syntax:
RETURN expr

The RETURN statement terminates execution of a stored function and
returns the value expr to the function caller. There must be at least
one RETURN statement in a stored function. There may be more than one
if the function has multiple exit points.

This statement is not used in stored procedures, triggers, or events.

URL: http://dev.mysql.com/doc/refman/5.1/en/return.html

