Syntax:
DROP {PROCEDURE | FUNCTION} [IF EXISTS] sp_name

This statement is used to drop a stored procedure or function. That is,
the specified routine is removed from the server. You must have the
ALTER ROUTINE privilege for the routine. (If the
automatic_sp_privileges system variable is enabled, that privilege and
EXECUTE are granted automatically to the routine creator when the
routine is created and dropped from the creator when the routine is
dropped. See
http://dev.mysql.com/doc/refman/5.5/en/stored-routines-privileges.html.
)

The IF EXISTS clause is a MySQL extension. It prevents an error from
occurring if the procedure or function does not exist. A warning is
produced that can be viewed with SHOW WARNINGS.

URL: http://dev.mysql.com/doc/refman/5.5/en/drop-procedure.html

