MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
DROP {PROCEDURE | FUNCTION} [IF EXISTS] sp_name
These statements are used to drop a stored routine (a stored
procedure or function). That is, the specified routine is removed
from the server. (DROP FUNCTION is also used to
drop loadable functions; see
Section 15.7.4.2, “DROP FUNCTION Statement for Loadable Functions”.)
To drop a stored routine, you must have the
ALTER ROUTINE privilege for it. (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
Section 27.2.2, “Stored Routines and MySQL Privileges”.)
In addition, if the definer of the routine has the
SYSTEM_USER privilege, the user
dropping it must also have this privilege. This is enforced in
MySQL 8.0.16 and later.
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.
DROP FUNCTION is also used to drop
loadable functions (see Section 15.7.4.2, “DROP FUNCTION Statement for Loadable Functions”).