Question

我有这样的查询

    CREATE  TRIGGER  check_shippeddate_tr
    ON  Orders
    FOR UPDATE
    AS
    IF      ((SELECT ShippedDate    FROM inserted) > (SELECT RequiredDate FROM Orders) )
                BEGIN
                                PRINT   'Order must be shipped before required date'
                                ROLLBACK TRANSACTION
                END
                GO

然而，当我尝试更新表时使用此代码

    UPDATE Orders
    SET ShippedDate = '1994-04-03'
    WHERE   OrderID = 11051
    AND     CustomerID = 'LAMAI'
    AND     EmployeeID = 7

它应该阻止更新并打印消息，因为ShippedDate位于RequiredDate之后。但是我收到了这个错误＆＃34; 子查询返回的值超过1。当子查询遵循=，！=，＆lt;，＆lt; =，＆gt;，＆gt; =或子查询用作表达式时，不允许这样做。＆＃34;我该如何解决？

Answer 1

尝试类似......

假设OrderID是主键列

CREATE  TRIGGER  check_shippeddate_tr
ON  Orders
FOR UPDATE
AS
BEGIN
  SET NOCOUNT ON;
IF EXISTS (SELECT 1 FROM inserted i 
           inner join Orders o ON i.OrderID = o.OrderID
           WHERE  i.ShippedDate > O.RequiredDate)
        BEGIN
                        PRINT   'Order must be shipped before required date'
                        ROLLBACK TRANSACTION
        END

END

Answer 2

在表格上创建一个检查约束

ALTER TABLE Orders 
ADD CHECK (ShippedDate < RequiredDate)

当子查询遵循＆gt;，＆gt; =或子查询用作表达式时，不允许这样做

2 个答案: