只更新表，如果字段为空

Question

我有这个疑问这是工作确定

UPDATE Master 
    SET Closed = Date(), 
     Status = 'Closed', 
     [Closure Reason] = 'Not on Extract' 
    WHERE NOT EXISTS (SELECT 1 
         FROM Extract 
         WHERE Master.Case = Extract.Case 
        ); 

我需要修改它添加另一个条件，即只做更新，如果主的价值。[关闭原因]为NULL

但是，这给出了一个语法错误：

UPDATE Master SET Closed = Date(), Status = 'Closed', [Closure Reason] = 'Not on Extract' 
WHERE [Closure Reason] = "" AND 
WHERE NOT EXISTS (SELECT 1 
        FROM Extract 
        WHERE Master.Case = Extract.Case 
       ); 

我已经尝试使用IS NULL而不是= “” 无济于事。

请问它有什么问题？

Answer 1

UPDATE Master SET Closed = Date(), Status = 'Closed', [Closure Reason] = 'Not on Extract' 
WHERE [Closure Reason] IS NULL 
AND NOT EXISTS (SELECT 1 
        FROM Extract 
        WHERE Master.Case = Extract.Case 
       ); 

您不能添加多个WHERE条款，您需要使用AND。如果您的要求是“只有在Master。[Closure Reason]为NULL”的情况下才进行更新，则检查NULL，而不是空字符串。

Answer 2

您需要在not exists之前删除第二个where。

UPDATE Master SET Closed = Date(), Status = 'Closed', [Closure Reason] = 'Not on Extract' 
WHERE [Closure Reason] = "" AND 
NOT EXISTS (SELECT 1 
        FROM Extract 
        WHERE Master.Case = Extract.Case 
       ); 

Answer 3

您需要添加的，而不是具有类似于

WHERE NOT EXISTS (SELECT 1 
        FROM Extract 
        WHERE Master.Case = Extract.Case 
       ) 
AND [Closure Reason] IS NULL;