Question

我正在使用SQL Server 2008 Management Studio。下面是我要编写的内容，我对第二个约束有一些困难。这有点令我困惑，我真的很感激一些帮助。

编写一个ALTER TABLE语句，该语句将两个新的检查约束添加到AP数据库的Invoices表中。第一个应该允许（1）PaymentDate仅在PaymentTotal为零时为空，并且（2）PaymentDate仅在PaymentTotal大于零时不为空。第二个约束应该防止PaymentTotal和CreditTotal的总和大于InvoiceTotal。

到目前为止，我所拥有的是第一个约束，但不是第二个，（PaymentTotal和CreditTotal的总和大于InvoiceTotal）。

ALTER TABLE Invoices WITH CHECK
ADD check (
    (PaymentTotal = 0 AND PaymentDate is NULL)
    OR
    (PaymentTotal > 0 AND PaymentDate is NOT NULL)
)
ADD CHECK (
    (PaymentTotal < InvoiceTotal = SUM)
    OR
    (CreditTotal < InvoiceTotal = SUM)
)

先谢谢你。

Answer 1

您编写了一个没有参数的聚合函数（SUM()）。

“第二个约束应该防止PaymentTotal和CreditTotal的总和大于InvoiceTotal。”这对我来说有点混乱，但是你应该把它改成：

ALTER TABLE Invoices WITH CHECK 
ADD check ( 
    (PaymentTotal = 0 AND PaymentDate is NULL) 
    OR 
    (PaymentTotal > 0 AND PaymentDate is NOT NULL) 
) 
go

ALTER TABLE Invoices WITH CHECK
ADD CHECK ( 
    (PaymentTotal + CreditTotal) <= InvoiceTotal 
) 
go

Answer 2

...
ADD CHECK (
    PaymentTotal + CreditTotal <= InvoiceTotal
)

SQL Server条件CHECK约束

2 个答案: