Question

CarID    Date             Shift
1        2016-08-20       3
1        2016-08-21       1
1        2016-08-21       2
2        2016-08-20       1
3        2016-08-21       3

预期结果

CarID    Date             Shift
1        2016-08-21       2
2        2016-08-20       1
3        2016-08-21       3

如何编写此类查询以获得最大日期和最大班次组合的每辆车的前1条记录？

Answer 1

您可以使用排名函数ROW_NUMBER，例如在CTE中：

WITH CTE AS
(
   SELECT RN = ROW_NUMBER() OVER (PARTITION BY CarID ORDER BY Date DESC, Shift DESC), *
   FROM dbo.TableName t
)
SELECT * FROM CTE
WHERE RN = 1

Answer 2

如果您想要同一行中的Date和Shift的最大值：

   select top 1 with ties CarId, [Date], Shift
     from myTable
    order by row_number() over (partition by CarId order by [Date] desc, Shift desc);

Answer 3

使用OUTER APPLY的另一种方法：

SELECT DISTINCT b.*
FROM YourTable a
OUTER APPLY (
    SELECT TOP 1 *
    FROM YourTable
    WHERE CarID=a.CarID
    ORDER BY [Date] DESC, [Shift] DESC) as b

输出：

CarID   Date        Shift
1       2016-08-21  2
2       2016-08-20  1
3       2016-08-21  3

如何根据3列选择前1名

3 个答案: