如何在触发器中访问INSERTED表的值？

例如：

INSERT INTO sales (sku, qty) 
VALUES
(1001, 5), //I need these values in the trigger
(1002, 1)
...

这是我的触发器：

DELIMITER $$

CREATE TRIGGER after_sales_insert 
AFTER INSERT ON sales 
FOR EACH ROW BEGIN

    UPDATE products
    SET NEW.qty = OLD.qty - INSERTED.qty
    WHERE sku = INSERTED.sku;

END;
$$
DELIMITER;

请注意,sales.sku是products表的外键.

SQL Server具有INSERTED关键字,这似乎不适用于MySQL.

回答：

NEW.qty引用设置触发器的表上的数量,而不是正在更新的表.

CREATE TRIGGER after_sales_insert 
AFTER INSERT ON sales 
FOR EACH ROW BEGIN

    UPDATE products
    SET qty = qty - NEW.qty
    WHERE sku = NEW.sku;

END;

解决方法:

鉴于：

INSERT INTO sales (sku, qty) 
VALUES
(1001, 5), //I need these values in the trigger
(1002, 1)
...

我相信你想要这个：

CREATE TRIGGER after_sales_insert AFTER INSERT ON sales 
FOR EACH ROW BEGIN
    UPDATE products
    SET qty = qty - NEW.qty
    WHERE sku = NEW.sku;
END;

参考文献：

> MySQL 8: 24.3.1 Trigger Syntax and Examples
> How to program a MySQL trigger to insert row into another table?
> How does “for each row” work in triggers in mysql?