数据库值得比较解决办法

数据库值得比较
有一个数据库表Test：
name types state times
A AA 1 2011-12-30 09:45:54
A AA 1 2011-12-30 09:45:54
A AA 1 2011-12-30 09:45:54
A BB 1 2011-12-30 09:45:54
A BB 1 2011-12-30 09:45:54
A BB 1 2011-12-30 09:45:54
A BB 1 2011-12-30 11:45:54
A AA 1 2011-12-30 11:45:54
A AA 2 2011-12-30 11:45:54
A AA 1 2011-12-30 11:45:54
A BB 1 2011-12-30 11:45:54
A BB 2 2011-12-30 11:45:54
A BB 1 2011-12-30 11:45:54
A BB 2 2011-12-30 11:45:54
要求：查询当前最大时间的数据和两小时前的最大时间的数据相比较，如果两小时前的state为1，而现在state为2，则显示现在最大时间时的值，上面的数据通过查询应显示成如下结果：

name types state times
A AA 2 2011-12-30 11:45:54
A BB 2 2011-12-30 11:45:54
A BB 2 2011-12-30 11:45:54



[解决办法]

SQL code

use Tempdbgo--> -->  if not object_id(N'Tempdb..#T1') is null    drop table #T1GoCreate table #T1([name] nvarchar(1),[types] nvarchar(2),[state] int,[times] Datetime)Insert #T1select N'A',N'AA',1,'2011-12-30 09:45:54' union allselect N'A',N'AA',1,'2011-12-30 09:45:54' union allselect N'A',N'AA',1,'2011-12-30 09:45:54' union allselect N'A',N'BB',1,'2011-12-30 09:45:54' union allselect N'A',N'BB',1,'2011-12-30 09:45:54' union allselect N'A',N'BB',1,'2011-12-30 09:45:54' union allselect N'A',N'BB',1,'2011-12-30 11:45:54' union allselect N'A',N'AA',1,'2011-12-30 11:45:54' union allselect N'A',N'AA',2,'2011-12-30 11:45:54' union allselect N'A',N'AA',1,'2011-12-30 11:45:54' union allselect N'A',N'BB',1,'2011-12-30 11:45:54' union allselect N'A',N'BB',2,'2011-12-30 11:45:54' union allselect N'A',N'BB',1,'2011-12-30 11:45:54' union allselect N'A',N'BB',2,'2011-12-30 11:45:54'GoSelect * ,[times2]=(SELECT MAX([times]) FROM #T1 where [name]=a.[name] AND [types]=a.[types] AND DATEDIFF(n,[times],a.[times])<120 AND state=1)from #T1 AS aWHERE [state]=2/*name    types    state    times    times2A    AA    2    2011-12-30 11:45:54.000    2011-12-30 11:45:54.000A    BB    2    2011-12-30 11:45:54.000    2011-12-30 11:45:54.000A    BB    2    2011-12-30 11:45:54.000    2011-12-30 11:45:54.000*/
[解决办法]
SQL code
create table tables(  a      nvarchar,   b      int,   c     nvarchar)insert into  tables Select  'A',2,'1'     union select 'A',3,'2'union SELECT 'a',1,'3'select  b.* from  (select a ,max(b) s from  tables               group by a )a,(select  * from  tables) bwhere a.a=b.a and a.s=b.b