获取分组中最新日期的行

Question

我有一张包含发票操作的表格。一张发票可以有多个操作。我需要为每张发票创建一个包含一行的视图。那一行应该是最新的行动。我目前有以下：

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，说明这是这样做的方法。但是我在结果集中得到多行具有相同的 TransNo？我错过了什么吗？

数据集：

结果运行查询：

我希望每笔交易只有一行。即使它有两个相同的日期，也应该只取一个。

Answer 1

对于此查询，您需要在日期上使用另一个连接条件：

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，我会推荐其他方法来执行此操作。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

Answer 2

我不推荐这种方法，但您需要在 join 中添加另一个条件：

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;

我会推荐窗口函数：

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
                   );