大家看看这个sql语句如何写?
数据如下,如何取得字段c(时间)最大的那批数据.
a                 b                     c
------------------------------------------
24168 4500.0000     2005-05-01   00:00:00
24168 5713.0000     2006-07-01   00:00:00
24169 3600.0000     2005-05-01   00:00:00
24169 4470.0000     2006-07-01   00:00:00
24170 3300.0000     2005-05-01   00:00:00
24170 4056.0000     2006-07-01   00:00:00
24171 3900.0000     2005-05-01   00:00:00
24171 5084.0000     2006-07-01   00:00:00
24173 4900.0000     2005-05-01   00:00:00


------解决方案--------------------
declare @t table(a int,b decimal(10,4),c datetime)
insert @t
select 24168, 4500.0000, '2005-05-01 00:00:00 ' union all
select 24168, 5713.0000, '2006-07-01 00:00:00 ' union all
select 24169, 3600.0000, '2005-05-01 00:00:00 ' union all
select 24169, 4470.0000, '2006-07-01 00:00:00 ' union all
select 24170, 3300.0000, '2005-05-01 00:00:00 ' union all
select 24170, 4056.0000, '2006-07-01 00:00:00 ' union all
select 24171, 3900.0000, '2005-05-01 00:00:00 ' union all
select 24171, 5084.0000, '2006-07-01 00:00:00 ' union all
select 24173, 4900.0000, '2005-05-01 00:00:00 '

select * from @t as t where not exists(select 1 from @t where a = t.a and c > t.c)

/*结果
a b c
----------- ------------ --------------------------
24168 5713.0000 2006-07-01 00:00:00.000
24169 4470.0000 2006-07-01 00:00:00.000
24170 4056.0000 2006-07-01 00:00:00.000
24171 5084.0000 2006-07-01 00:00:00.000
24173 4900.0000 2005-05-01 00:00:00.000
*/
------解决方案--------------------
--方法一
Select * From 表 A Where Not Exists(Select c From 表 Where a = A.a And c > A.c)

--方法二
Select * From 表 A Where c = (Select Max(c) From 表 Where a = A.a)

--方法三
Select A.* From 表 A
Inner Join
(Select a, Max(c) As c From 表 Group By a) B
On A.a = B.a And A.c = B.c