創建觸發器語句

 CREATE TRIGGER

CREATE
    [DEFINER = user]
    TRIGGER trigger_name
    trigger_time trigger_event
    ON tbl_name FOR EACH ROW
    [trigger_order]
    trigger_body

trigger_time: { BEFORE | AFTER }

trigger_event: { INSERT | UPDATE | DELETE }

trigger_order: { FOLLOWS | PRECEDES } other_trigger_name

 DROP TRIGGER

DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name

https://dev.mysql.com/doc/refman/5.7/en/create-trigger.html