SQL CHECK约束问题

Question

我正在使用SQL Server 2008，我有一个包含三列的表：Length,StartTime和EndTime。我想就这个表，说CHECK约束：

if Length == NULL then 
    StartTime <> NULL and EndTime <> NULL 
else 
    StartTime == NULL and EndTime == NULL 

我已经开始尝试这样的事情：

Length == NULL AND StartTime <> NULL AND EndTime <> NULL 

这显然是不够的，但即使这样简单的表达式不验证。我得到的错误：

"Error validating 'CK_Test_Length_Or_Time'. Do you want to edit the constraint?"

任何想法如何去做到这一点？

Answer 1

SQL Server中没有==运算符。虽然检查空，你必须用 “是”

请试试这个：

((Length is null AND starttime is not null AND endtime is not null) OR 
(Length is not null AND starttime is null AND endtime is null)) 

HTH

Answer 2

CHECK ([Length] IS NULL AND [StartTime] IS NOT NULL AND [EndTime] IS NOT NULL 
     OR [Length] IS NOT NULL AND [StartTime] IS NULL AND [EndTime] IS NULL))