# MySQL TRIGGER


* OLD 與 NEW
* 「OLD.欄位名稱」: 修改或刪除前的欄位值
* 「NEW.欄位名稱」: 修改後或新增的欄位值
* 範例：使用 OLD 保存将要被删除的行到一个存档表中

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;

* 範例：保证更新州名缩写总是大写（不管UPDATE语句中给出的是大写还是小写）

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

###### tags: `MySQL`