sql-server - 仅当另一列也相同时，是否可以使用 ROW_NUMBER() OVER/PARTITION BY？

Question

我正在使用这段代码：（来自这个问题：如何在 SQL 中获取每组的最后一条记录，替换我自己的列）

WITH e AS
(
 SELECT *,
     ROW_NUMBER() OVER
     (
         PARTITION BY ApplicationId
         ORDER BY theDate DESC
     ) AS Recency
 FROM [Event]
)
SELECT *
FROM e
WHERE Recency = 1

只有当两个字段相同时才可以“分区”吗？例如我有这样的数据：

ID      Name    theDate
123     John    01/01/2012
123     John    01/02/2012
123     Doe     01/01/2012
456     Smith   02/04/2012
789     Smith   02/01/2012
789     Smith   02/09/2012
789     Roger   02/08/2012

从我想返回的数据中：

ID      Name    theDate
123     John    01/02/2012
123     Doe     01/01/2012
456     Smith   02/04/2012
789     Smith   02/09/2012
789     Roger   02/08/2012

谢谢你的帮助。

托马斯

Answer 1

您可以有几列用逗号分隔

WITH e AS 
( 
 SELECT *, 
     ROW_NUMBER() OVER 
     ( 
         PARTITION BY ApplicationId , Name
         ORDER BY theDate DESC 
     ) AS Recency 
 FROM [Event] 
) 
SELECT * 
FROM e 
WHERE Recency = 1 

Answer 2

我在这里找到了答案：Table partitioning using 2 columns

您只能在 1 列上进行分区，但是可以生成该列以创建“多分区”，如下所示：

WITH e AS 
( 
 SELECT *, 
 ROW_NUMBER() OVER 
 ( 
     PARTITION BY CONVERT(VARCHAR(100),ApplicationId) + ' ' + Name
     ORDER BY theDate DESC 
 ) AS Recency 
 FROM [Event] 
) 
SELECT * 
FROM e 
WHERE Recency = 1 

将两列加在一起作为一个字符串可确保仅在两列相同时才进行分区。