SQL

Triggers in MySQL example

delimiter //
CREATE TRIGGER person_ai AFTER INSERT
ON person
FOR EACH ROW
UPDATE average_age SET average = (SELECT AVG(age) FROM person); //
delimiter ;

trigger in mysql syntax

CREATE TRIGGER trigger_name
{BEFORE | AFTER} {INSERT | UPDATE| DELETE }
ON table_name FOR EACH ROW
trigger_body;

Triggers in MySQL example

delimiter //
CREATE TRIGGER person_bu BEFORE UPDATE
ON person
FOR EACH ROW
IF NEW.age < 18 THEN
SIGNAL SQLSTATE '50002' SET MESSAGE_TEXT = 'Person must be older than 18.';
END IF; //
delimiter ;

trigger in mysql

CREATE TRIGGER Product_Details_tr 
BEFORE INSERT ON Product_Details 
FOR EACH ROW 
SET NEW.User_ID = CURRENT_USER();

Triggers in MySQL example

delimiter //
CREATE TRIGGER person_bi BEFORE INSERT
ON person
FOR EACH ROW
IF NEW.age < 18 THEN
SIGNAL SQLSTATE '50001' SET MESSAGE_TEXT = 'Person must be older than 18.';
END IF; //
delimiter ;

triggers in mysql

A trigger is a set of codes that executes in response to some events.