凡在SQL子句

Question

我的SQL查詢如下

IF @StatusId = 10 
    BEGIN 
     SELECT 
      * 
     FROM 
     Risk AS R 
     INNER JOIN Statuses AS St ON R.Status_Id=St.Status_Id 
     WHERE 
     R.MitigationOwner = COALESCE(@MitigationOwner,R.MitigationOwner) 
     AND R.RiskFactor = COALESCE(@RiskFactor,R.RiskFactor) 
     AND R.RiskArea = COALESCE(@RiskArea,R.RiskArea) 
     AND R.AddedWhen BETWEEN 
     COALESCE(CONVERT(DATETIME, @StartDate+'00:00:00',120),R.AddedWhen) AND 
     COALESCE(CONVERT(DATETIME,@EndDate+'23:59:59',120),R.AddedWhen) 
    END 

當我只傳遞狀態標識及所有其它變量爲空，然後用NULL MitigationOwner或ModifiedDate記錄不會顯示.. 什麼是錯的這個查詢？

Answer 1

我相信，通過ModifiedDate你的意思是R.AddedWhen

試試這個：

SELECT 
      * 
     FROM 
     Risk AS R 
     INNER JOIN Statuses AS St ON R.Status_Id=St.Status_Id 
     WHERE 
     (R.MitigationOwner = COALESCE(@MitigationOwner,R.MitigationOwner) OR R.MitigationOwner IS NULL) 
     AND R.RiskFactor = COALESCE(@RiskFactor,R.RiskFactor) 
     AND R.RiskArea = COALESCE(@RiskArea,R.RiskArea) 
     AND (R.AddedWhen BETWEEN 
     COALESCE(CONVERT(DATETIME, @StartDate+'00:00:00',120),R.AddedWhen) AND 
     COALESCE(CONVERT(DATETIME,@EndDate+'23:59:59',120),R.AddedWhen) OR R.AddedWhen IS NULL) 

Answer 2

使用形式：

... 
(R.MitigationOwner = @MitigationOwner OR @MitigationOwner IS NULL) 
... 

這是在SQL Server優化。 COALESCE不是。

編輯：這不一樣的保羅·威廉斯的答案，但他的回答讓明確的‘NULL = NULL’相匹配。 mlogic更簡單，因爲NULL永遠不會等於NULL。

Answer 3

如果R.MitigationOwner可以爲空，那麼你比較子句：

WHERE 
R.MitigationOwner = COALESCE(@MitigationOwner,R.MitigationOwner) 

必須重寫，以處理空值：

WHERE 
((R.MitigationOwner IS NULL AND @MitigationOwner IS NULL) 
OR (R.MitigationOwner = @MitigationOwner)) 

見this article on Wikipedia about NULL。