Guarantee that user cannot insert a manual id on a auto_increment field

remove_manual_id_trigger.sql

DROP TRIGGER IF EXISTS sakila.bf_insert_actor;

DELIMITER $$

CREATE TRIGGER bf_insert_actor
 BEFORE INSERT ON sakila.actor
 FOR EACH ROW
 BEGIN
 	IF NEW.actor_id IS NOT NULL THEN
 		SET NEW.actor_id = null;
	END IF;
END $$