Question

我知道以前曾经问过这个问题，但我似乎无法找到合适的解决方案。

我有这些数据：

Label           StartDate     ActivityKey
------------------------------------------------------------------
LABELS          2009-02-12    23D645CA-7F05-47FF-9AC4-1414DCBF44DD
LABELS          2010-11-01    C266A254-2A3D-4A37-8281-AE9EA08ED086
MASTER BOXES    2009-02-12    81DBEA52-B7BC-4861-96B4-7A77A2D7F07B
MASTER BOXES    2010-11-01    9DAD9F77-46FD-4694-9168-E4E5FE306B7D

我只想要每个Label的最新版本。这是理想的：

Label           StartDate     ActivityKey
------------------------------------------------------------------
LABELS          2010-11-01    C266A254-2A3D-4A37-8281-AE9EA08ED086
MASTER BOXES    2010-11-01    9DAD9F77-46FD-4694-9168-E4E5FE306B7D

感谢您提供任何提示

（顺便说一句，这是SQL Server 2008）

Answer 1

SELECT label, StartDate, ActivityKey
    FROM (SELECT label, StartDate, ActivityKey,
                 ROW_NUMBER() OVER (PARTITION BY label ORDER BY StartDate DESC) AS RowNum
              FROM YourTable
         ) t
    WHERE t.RowNum = 1

也可以使用CTE：

完成相同的查询

WITH cteRowNum AS (
    SELECT label, StartDate, ActivityKey,
           ROW_NUMBER() OVER (PARTITION BY label ORDER BY StartDate DESC) AS RowNum
        FROM YourTable
)
SELECT label, StartDate, ActivityKey
    FROM cteRowNum
    WHERE RowNum = 1

Answer 2

这也是另一种选择...... :)

Select T.label, T.StartDate, T1.ActivityKey From
(
    Select label, Max(StartDate) as StartDate
    From YourTable
    Group By label
)T
Inner Join YourTable T1 on T1.Label = T.Label and T1.StartDate = T.StartDate

当密钥完全不同时，如何获取最新的行？

2 个答案: