重复记录的取最新一笔

一位网友在Insus.NET下班时问及一个SQL问题，他有如下一些记录：

S_NUMBER       P_NO     UPDATE_TIME
Y1202022524   E3465   2012-02-05 16:32:16.000
Y1202022524   E0035   2012-01-16 05:38:41.000
Y1202022525   E0036   2012-01-17 05:38:41.000
Y1202022526   E0037   2012-01-18 05:38:41.000
Y1202022527   E0038   2012-01-19 05:38:41.000
Y1202022528   E0039   2012-01-20 05:38:41.000
Y1202022529   E0040   2012-01-21 05:38:41.000

要SELECT所有记录，过滤所有重复[S_NUMBER]的记录，只取[UPDATE_TIME]最新的一笔。

下面是Insus.NET帮他解决的方法与过程：

创建一个临时表#Data

CREATE TABLE [#Datas]
(
    S_NUMBER NVARCHAR(30),
    P_NO NVARCHAR(30),
    UPDATE_TIME DATETIME
)

把数据插入这个临时表中：

INSERT INTO [#Datas] VALUES 
('Y1202022524', 'E3465', '2012/02/05 16:32:16'),
('Y1202022524', 'E0035', '2012/01/16 05:38:41'),
('Y1202022525', 'E0036', '2012/01/17 05:38:41'),
('Y1202022526', 'E0037', '2012/01/18 05:38:41'),
('Y1202022527', 'E0038', '2012/01/19 05:38:41'),
('Y1202022528', 'E0039', '2012/01/20 05:38:41'),
('Y1202022529', 'E0040', '2012/01/21 05:38:41')

GO

下面SELECT是在MS SQL Server 2008 R2查询分析器实现：

WITH it([S_NUMBER],[UPDATE_TIME])
AS
(
    SELECT [S_NUMBER],MAX([UPDATE_TIME]) FROM [dbo].[#Datas] GROUP BY [S_NUMBER]    
)
SELECT DISTINCT d.[S_NUMBER],[P_NO],d.[UPDATE_TIME] 
FROM [dbo].[#Datas] AS d 
INNER JOIN it
 ON (d.[S_NUMBER] = it.[S_NUMBER] and d.[UPDATE_TIME] = it.[UPDATE_TIME]);

执行结果：