SQL Server：仅选择具有MAX（DATE）的行

我有一个数据表（数据库是MSSQL）：

    ID  OrderNO PartCode  Quantity DateEntered
    417 2144     44917    100      18-08-11
    418 7235     11762    5        18-08-11
    419 9999     60657    100      18-08-11
    420 9999     60657    90       19-08-11

我想查询一个返回OrderNO，PartCode和Quantity的查询，但仅返回最后一次注册的订单。

我想从示例表中获取以下信息：

     OrderNO PartCode  Quantity     
     2144     44917    100      
     7235     11762    5        
     9999     60657    90      

请注意，订单9999只返回了一行。

谢谢！

如果rownumber() over(...)适合您....

select OrderNO,
       PartCode,
       Quantity
from (select OrderNO,
             PartCode,
             Quantity,
             row_number() over(partition by OrderNO order by DateEntered desc) as rn
      from YourTable) as T
where rn = 1      

如果ROW_NUMBER()可以的话，最好的方法是Mikael Eriksson 。

其次，按照Cularis的答案加入查询。

或者，最简单直接的方法是WHERE子句中的相关子查询。

SELECT
  *
FROM
  yourTable AS [data]
WHERE
  DateEntered = (SELECT MAX(DateEntered) FROM yourTable WHERE orderNo = [data].orderNo)

要么...

WHERE
  ID = (SELECT TOP 1 ID FROM yourTable WHERE orderNo = [data].orderNo ORDER BY DateEntered DESC)

select OrderNo,PartCode,Quantity
from dbo.Test t1
WHERE EXISTS(SELECT 1
         FROM dbo.Test t2
         WHERE t2.OrderNo = t1.OrderNo
           AND t2.PartCode = t1.PartCode
         GROUP BY t2.OrderNo,
                  t2.PartCode
         HAVING t1.DateEntered = MAX(t2.DateEntered))

这是上面提供的所有查询中最快的。查询成本为0.0070668。

上面的首选答案由Mikael Eriksson提出，查询成本为0.0146625

您可能并不关心这么小的样本的性能，但是在大的查询中，所有这些加起来。

SELECT t1.OrderNo, t1.PartCode, t1.Quantity
FROM table AS t1
INNER JOIN (SELECT OrderNo, MAX(DateEntered) AS MaxDate
            FROM table
            GROUP BY OrderNo) AS t2
ON (t1.OrderNo = t2.OrderNo AND t1.DateEntered = t2.MaxDate)

内部查询将选择所有OrderNo具有其最大日期的日期。要获取该表的其他列，您可以将它们连接到OrderNo和上MaxDate。

对于MySql，您可以执行以下操作：

select OrderNO, PartCode, Quantity from table a
join (select ID, MAX(DateEntered) from table group by OrderNO) b on a.ID = b.ID

您还可以将该select语句用作左联接查询...示例：

... left join (select OrderNO,
   PartCode,
   Quantity from (select OrderNO,
         PartCode,
         Quantity,
         row_number() over(partition by OrderNO order by DateEntered desc) as rn
  from YourTable) as T where rn = 1 ) RESULT on ....

希望这对搜索此内容的人有所帮助:)

rownumber（）over（...）正在工作，但由于两个原因，我不喜欢此解决方案。-当您使用旧版本的SQL（例如SQL2000）时，此功能不可用。-对功能的依赖关系，并且无法真正读取。

另一个解决方案是：

SELECT tmpall.[OrderNO] ,
       tmpall.[PartCode] ,
       tmpall.[Quantity] ,
FROM   (SELECT [OrderNO],
               [PartCode],
               [Quantity],
               [DateEntered]
        FROM   you_table) AS tmpall
       INNER JOIN (SELECT [OrderNO],
                          Max([DateEntered]) AS _max_date
                   FROM   your_table
                   GROUP  BY OrderNO ) AS tmplast
               ON tmpall.[OrderNO] = tmplast.[OrderNO]
                  AND tmpall.[DateEntered] = tmplast._max_date

如果您已为ID和OrderNo编制了索引，则可以使用IN ：（我不愿为避免混淆而简化交易，只是为了节省一些周期）：

select * from myTab where ID in(select max(ID) from myTab group by OrderNo);

尽量避免在使用中加入

SELECT SQL_CALC_FOUND_ROWS *  FROM (SELECT  msisdn, callid, Change_color, play_file_name, date_played FROM insert_log
   WHERE play_file_name NOT IN('Prompt1','Conclusion_Prompt_1','silent')
 ORDER BY callid ASC) t1 JOIN (SELECT MAX(date_played) AS date_played FROM insert_log GROUP BY callid) t2 ON t1.date_played=t2.date_played

这对我来说非常好。

    select name, orderno from (
         select name, orderno, row_number() over(partition by 
           orderno order by created_date desc) as rn from orders
    ) O where rn =1;

这对我有用。使用MAX（CONVERT（date，ReportDate））确保您具有日期值

select max( CONVERT(date, ReportDate)) FROM [TraxHistory]