《MySQL必知必会》第二十五章-使用触发器

触发器是MySQL响应以下任意语句而自动执行的一条MySQL语句：

• DELETE
• INSERT
• UPDATE

其他MySQL语句不支持触发器，只有表才支持触发器，视图不支持（临时表也不支持）

创建触发器

CREATE TRIGGER newproduct AFTER INSERT ON products
FOR EACH ROW SELECT 'Product added';

删除触发器

DROP TRIGGER newproduct;

使用触发器

INSERT触发器

CREATE TRIGGER neworder AFTER INSERT ON orders
FOR EACH ROW SELECT NEW.order_num;
-- INSERT INTO orders(order_date, cust_id)
-- VALUES(Now(), 10001);

DELETE触发器

DELIMITER //
CREATE TRIGGER deleteorder BEFORE DELETE ON orders
FOR EACH ROW
BEGIN
    INSERT INTO archive_orders(order_num, order_date, cust_id)
    VALUES(OLD.order_num, OLD.order_date, OLD.cust_id);
END//
DELIMITER ;

UPDATE触发器

CREATE TRIGGER updatevendor BEGORE UPDATE ON vendors
FOR EACH ROW SET NEW.vend_state = Upper(New.vend_state);