Question

我想总结一个案例的发生。我试图在案例陈述中使用总和，但我得到了这个错误，怎么解决？

Msg 130, Level 15, State 1, Line 3
Cannot perform an aggregate function on an expression containing an aggregate or a subquery.

我的代码示例：

select 
sum(case when cast(max(ptl.RowDate)as int) = cast(Min(ptl.RowDate) as int) then 1 else 0 end)
,DATEPART(WEEK, rowdate) week_
from m.dbo.tblLog ptl (nolock)
where rowdate > GETDATE()-91
group by DATEPART(WEEK, rowdate)

更新：基于评论：我想计算仅访问网页的不同用户一次。我希望根据每周时间框架获取计数。

Answer 1

您不能在另一个内部使用聚合函数。您需要使用子查询或CTE：

SELECT  SUM(something) as s,
        week_
FROM (
    select  case when cast(max(ptl.RowDate)as int) = cast(Min(ptl.RowDate) as int) then 1 else 0 end as something,
            DATEPART(WEEK, rowdate) week_
    from m.dbo.tblLog ptl (nolock)
    where rowdate > GETDATE()-91
    group by DATEPART(WEEK, rowdate)
    ) as res
GROUP BY week_

Answer 2

查询的替代方式

SELECT SUM(CASE WHEN CAST(MaxRowDate AS INT) = cast(MinRowDate AS INT) THEN 1 ELSE 0 END)
week_
FROM
(

  SELECT MAX(ptl.RowDate) MaxRowDate,MIN(ptl.RowDate) MinRowDate,DATEPART(WEEK, rowdate) week_
  FROM m.dbo.tblLog ptl (NOLOCK)
  WHERE rowdate > GETDATE()-91
  GROUP BY DATEPART(WEEK, rowdate)
 )M   
 GROUP BY week_

Answer 3

如果您只想要一面旗帜，为什么还要sum()：

select (case when cast(max(ptl.RowDate)as int) = cast(Min(ptl.RowDate) as int) 
             then 1 else 0
        end) as OneValueFlag,
       DATEPART(WEEK, rowdate) as week_
from m.dbo.tblLog ptl (nolock)
where rowdate > GETDATE() - 91
group by DATEPART(WEEK, rowdate);

还完全不清楚为什么将价值转换为日期：

select (case when max(ptl.RowDate) = Min(ptl.RowDate)
             then 1 else 0
        end) as OneValueFlag,
       DATEPART(WEEK, rowdate) as week_
from m.dbo.tblLog ptl (nolock)
where rowdate > GETDATE() - 91
group by DATEPART(WEEK, rowdate);

我可以在最大/最小函数上使用sum和case语句吗？

3 个答案: