Sql Group By Max Value在一列中

Question

我一整天都在拔头发，有人可以帮我。 我认为它可能很简单，但我不能完全得到我想要的东西。

表中的数据如下所示

CallId      ProblemDescription  CurrentAction     CurrentEngineer    EventNumber
CON-00002                       Respond to Call                      0
WHS-00001                       Respond to Call                      0
WHS-00002                       Respond to Call                      0
WHS-00003                       Respond to Call                      0
WHS-00003                       Fix Problem                          1
WHS-00003                       Problem Fixed                        2

我想要做的是显示具有最大事件编号的CallId的所有列。 即

CallId      ProblemDescription  CurrentAction     CurrentEngineer    EventNumber
CON-00002                       Respond to Call                      0
WHS-00001                       Respond to Call                      0
WHS-00002                       Respond to Call                      0
WHS-00003                       Problem Fixed                        2

但是，我无法弄清楚如何做到这一点。

目前我正在使用

Select CallId, MAX(ProblemDescription), MAX(CurrentAction), MAX(CurrentEngineer),
MAX(EventNumber) FROM [Table] GROUP BY CallId

这显然如何为每个coloumn单独返回最大值。 因此，在上面的情况下，CurrentAction列显示Respond to Call未Respond to Call

任何人都可以告诉我如何做到这一点???

谢谢

Answer 1

我假设您正在寻找DENSE_RANK ：

WITH CTE AS
(
   SELECT 
      CallId, 
      ProblemDescription, 
      CurrentAction, 
      CurrentEngineer, 
      EventNumber,
      Rank = DENSE_RANK() OVER (PARTITION BY CallId ORDER BY EventNumber DESC)
   FROM dbo.TableName
)
SELECT 
   CallId, ProblemDescription, CurrentAction, CurrentEngineer, EventNumber
FROM 
   CTE
WHERE 
   RANK = 1

如果每个CallId只需要一行，即使有多个具有相同的最大EventNumber使用ROW_NUMBER 。

Answer 2

你想使用row_number（）：

select CallId, ProblemDescription, CurrentAction, CurrentEngineer, EventNumber
from (select t.*,
             ROW_NUMBER() over (partition by callId order by eventnumber desc) as seqnum
      from t
     ) t
where seqnum = 1

Answer 3

使用此代码。 *仅在事件编号列上使用Max聚合。

SELECT CallID, Problem_Description, Current_Action, Current_Engineer, MAX( Event_Number ) FROM test.data GROUP BY CallID;

这可能对你有帮助