在分组依据中获取最新日期的行

问题描述

我有带有发票操作的表。一张发票可以有多个动作。我需要为每个发票创建一个带有一行的视图。该行应该是最新动作。我目前正在关注：

SELECT  tbl.*
FROM [dbo].[Tester] tbl JOIN
      (SELECT TransNo,MAX(TransDate) AS MxDt
       FROM [dbo].[Tester]
       GROUP BY TransNo
      ) sub
      ON tbl.TransNo = sub.TransNo AND TransDate = MxDt;

我在这里看到了多个帖子，指出这是做到这一点的方法。但是我在结果集中得到了多行相同的TransNo吗？我错过了什么吗？

数据集：

运行结果查询：

我希望每笔交易只有一行。即使有两个日期相同的日期，也应该只取一个。

解决方法

我不推荐这种方法，但是您需要在join中使用另一个条件：

SELECT  tbl.TransNo
FROM [clm].[InvoiceView] tbl JOIN
      (SELECT TransNo,MAX(ActDate) AS MxDt
       FROM [clm].[InvoiceView]
       GROUP BY TransNo
      ) sub
      ON tbl.TransNo = sub.TransNo AND ActDate = MxDt;

相反，我建议使用窗口功能：

select iv.*
from (select iv.*,row_number() over (partition by transno order by actdate desc) as seqnum
      from InvoiceView iv
     ) iv
where seqnum = 1;

或：

select iv.*
from InvoiceView iv
where iv.actdate = (select max(iv2.date)
                    from InvoiceView iv2
                    where iv2.transno = iv.transno
                   );

,

对于此查询，您需要日期上的另一个加入条件：

SELECT  tbl.TransNo
FROM [clm].[InvoiceView] tbl
INNER JOIN (
    SELECT  TransNo,MAX(ActDate) AS [MxDt]
    FROM [clm].[InvoiceView]
    GROUP BY TransNo
) sub ON tbl.TransNo = sub.TransNo AND tbl.ActDate = sub.[MxDt]
                      -----------> here

但是，我建议还有其他方法可以做到这一点。一种选择是row_number()：

select *
from (
    select iv.*,row_number() over(partition by transno order by actdate desc) rn
    from [clm].[InvoiceView] iv
) iv
where rn = 1