MySQL triggers are procedures that fire when certain events occur, such as inserting, deleting, changing a string.
An example of viewing triggers:
SHOW TRIGGERS\G;
Example of removing a trigger:
DROP TRIGGER name;
Triggers can be executed both before and after the execution of the request (BEFORE / AFTER).
Trigger Syntax:
CREATE TRIGGER `name` BEFORE/AFTER INSERT/UPDATE/DELETE ON `database`.`table` FOR EACH ROW BEGIN -- trigger body END;
An example of creating a trigger:
DELIMITER // CREATE TRIGGER next_contract_id BEFORE INSERT ON users_pi FOR EACH ROW BEGIN IF NEW.contract_id = '' THEN SET NEW.contract_id=NEW.uid; END IF; IF NEW.contract_date = '' or NEW.contract_date = '0000-00-00' THEN SET NEW.contract_date=curdate(); END IF; END; // DELIMITER ;