只更新表，如果字段爲空

Question

我有這個疑問這是工作確定

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個條件，即只做更新，如果主的價值。[關閉原因]爲NULL

但是，這給出了一個語法錯誤：

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 
       ); 

我已經嘗試使用IS NULL而不是= 「」 無濟於事。

請問它有什麼問題？

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 
       ); 

您不能添加多個WHERE條款，您需要使用AND。如果您的要求是「只有在Master。[Closure Reason]爲NULL」的情況下才進行更新，則檢查NULL，而不是空字符串。

Answer 2

您需要在not exists之前刪除第二個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，而不是具有類似於

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