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Id并且所有其他变量都为null时，不会显示包含NULL MitigationOwner或ModifiedDate的记录。这个查询有什么问题？

Answer 1

使用表格：

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

这在SQL Server中进行了优化。 COALESCE不是。

编辑：这与Paul Williams的回答相同，但他的回答允许明确的“NULL = NULL”匹配。 m ylogic更简单，因为NULL永远不等于NULL。

Answer 2

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 3

如果R.MitigationOwner可以为null，那么您的比较子句：

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

必须重写以处理NULL值：

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

请参阅this article on Wikipedia about NULL。

sql中的where子句

3 个答案: