SQL触发器使用多个表

时间:2014-01-27 00:03:27

标签: sql triggers

问题

编写SQL命令以在表Order中创建触发器。触发器应在每次产品出现在订单表中的新订单行之后,从产品表的quantityRemaining列中减去订单中产品的数量。

表格

CREATE TABLE Product(
productNo int PRIMARY KEY,
productName VARCHAR(30),
quantityRemaining INT,
cost DECIMAL (10,2) DEFAULT 0.00);

CREATE TABLE Orders(
orderNo INT PRIMARY KEY,
custNo INT CONSTRAINT cusNo_fk REFERENCES CustomerDetails(custNo) ON DELETE CASCADE,
productNo INT CONSTRAINT prodNo_fk REFERENCES Product(productNo) ON DELETE CASCADE,
quantity INT);

尝试

CREATE OR REPLACE TRIGGER subtractQuantity 
AFTER INSERT ON Orders
FOR EACH ROW

BEGIN
     UPDATE Product
     SET quantityRemaining = quantityRemaining - quantity
     WHERE productNo = :NEW.ProductNo;
END;
/

错误

它无法识别'数量'变量。

1 个答案:

答案 0 :(得分:3)

我认为您缺少:New.作为参考:

CREATE OR REPLACE TRIGGER subtractQuantity 
AFTER INSERT ON Orders
FOR EACH ROW

BEGIN
     UPDATE Product
     SET quantityRemaining = quantityRemaining - :NEW.quantity
     WHERE productNo = :NEW.ProductNo;
END;

quantity位于Orders表中,而不是Product表。