MySQL Trigger
CREATE TABLE test1(a1 INT);
CREATE TABLE test2(a2 INT);
CREATE TABLE test3(a3 INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
CREATE TABLE test4(
a4 INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
b4 INT DEFAULT 0
);
delimiter //
CREATE TRIGGER name_of_trigger [BEFORE|AFTER] [INSERT|UPDATE|DELETE]
ON test1
FOR EACH ROW
BEGIN
/*
Examples of code to write
*/
[INSERT|DELETE|UPDATE|IF|ELSEIF|END IF];
/*
NEW.a1 meanse the new value that will be added with INSERT into test1
*/
INSERT INTO test2 SET a2 = NEW.a1;
DELETE FROM test3 WHERE a3 = NEW.a1;
UPDATE test4 SET b4 = b4 + 1 WHERE a4 = NEW.a1;
IF NEW.a1 < 0 THEN
SET NEW.a1 = 0;
ELSEIF NEW.a1 > 100 THEN
SET NEW.a1 = 100;
END IF;
END//
delimiter;
Hou