将数据 分组,取得日期最大的记录,如果日期最大有相同 就一起取
如下:
ID Date
1 2012-3-10
1 2012-3-10
1 2012-3-4
2 2012-2-10
2 2012-2-10
2 2012-3-8
2 2012-3-9
3 2012-5-12
3 2012-4-12
3 2012-1-2
4 2012-5-5
5 2012-3-7
6 2012-4-2
7 2012-2-1
要 获得这样的结果:
ID Date
1 2012-3-10
1 2012-3-10
2 2012-3-9
3 2012-5-12
4 2012-5-5
5 2012-3-7
6 2012-4-2
7 2012-2-1
------解决方案--------------------
SELECT * FROM TB T WHERE DATE=(SELECT MAX(DATE) FROM TB WHERE ID=T.ID)
------解决方案--------------------
1楼的结果不对
WITH test (ID, [Date])
AS
(
SELECT 1, '2012-3-10'
UNION ALL SELECT 1, '2012-3-10'
UNION ALL SELECT 1, '2012-3-4'
UNION ALL SELECT 2, '2012-2-10'
UNION ALL SELECT 2, '2012-2-10'
UNION ALL SELECT 2, '2012-3-8'
UNION ALL SELECT 2, '2012-3-9'
UNION ALL SELECT 3, '2012-5-12'
UNION ALL SELECT 3, '2012-4-12'
UNION ALL SELECT 3, '2012-1-2'
UNION ALL SELECT 4, '2012-5-5'
UNION ALL SELECT 5, '2012-3-7'
UNION ALL SELECT 6, '2012-4-2'
UNION ALL SELECT 7, '2012-2-1'
)
SELECT id,MIN ([Date])[Date]
FROM Test
GROUP BY id
/*
id Date
----------- ---------
1 2012-3-10
2 2012-2-10
3 2012-1-2
4 2012-5-5
5 2012-3-7
6 2012-4-2
7 2012-2-1
(7 行受影响)
*/
------解决方案--------------------
--DROP TABLE #TB
SELECT 1 AS ID, CONVERT(DATETIME,'2012-3-10') DATE INTO #TB
UNION ALL SELECT 1, '2012-3-10'
UNION ALL SELECT 1, '2012-3-4'
UNION ALL SELECT 2, '2012-2-10'
UNION ALL SELECT 2, '2012-2-10'
UNION ALL SELECT 2, '2012-3-8'
UNION ALL SELECT 2, '2012-3-9'
UNION ALL SELECT 3, '2012-5-12'