凡在SQL子句

Question

我的SQL查询如下

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 

当我只传递状态标识及所有其它变量为空，然后用NULL MitigationOwner或ModifiedDate记录不会显示.. 什么是错的这个查询？

Answer 1

我相信，通过ModifiedDate你的意思是R.AddedWhen

试试这个：

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) 
... 

这是在SQL Server优化。 COALESCE不是。

编辑：这不一样的保罗·威廉斯的答案，但他的回答让明确的‘NULL = NULL’相匹配。 mlogic更简单，因为NULL永远不会等于NULL。

Answer 3

如果R.MitigationOwner可以为空，那么你比较子句：

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

必须重写，以处理空值：

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

见this article on Wikipedia about NULL。