如何取相同ID中首条记录？

[zhengjialon]

有某表：
ID 子ID 客户名 客户订单号 金额
1 1 aaa 10001 1000
1 2 bbb 20002 2000
1 3 ccc 30004 1140
2 1 www 10100 3000
2 2 qqq 32000 4500

得到结果：
ID 子ID 客户名 客户订单号 金额
1 1 aaa 10001 1000
2 1 www 10100 3000

[whiteyundd]

select * from(
select *,ROW_NUMBER() over(PARTITION BY id order by 子ID) rn from tb
) t
where rn=1

[appleller]

select * from tb a where not exists (select 1 from tb where id=a.id
and 子ID <a.子ID )

[昵称被占用了]

select * from tb a
where not exists (
select 1 from tb
where id=a.id
and 子ID  <a.子ID  
)

[playwarcraft]

select * from T as A
where not exists(select 1 from T where ID=A.ID and 子ID<A.子ID)

[jiangshun]

-----------------------------------------

--> 测试时间：2009-07-15
--> 我的淘宝：http://shop36766744.taobao.com/

--------------------------------------------------

if object_id('[tb]') is not null drop table [tb]
create table [tb]([ID] int,[子ID] int,[客户名] varchar(3),[客户订单号] int,[金额] int)
insert [tb]
select 1,1,'aaa',10001,1000 union all
select 1,2,'bbb',20002,2000 union all
select 1,3,'ccc',30004,1140 union all
select 2,1,'www',10100,3000 union all
select 2,2,'qqq',32000,4500

select * from [tb] t where not exists(select 1 from tb where T.id=id and T.子ID>子ID)
/*
ID          子ID         客户名  客户订单号       金额          
----------- ----------- ---- ----------- ----------- 
1           1           aaa  10001       1000
2           1           www  10100       3000

（所影响的行数为 2 行）

*/

drop table TB

[playwarcraft]

--SQL2005

select ID ,子ID  ,客户名, 客户订单号, 金额
from
(select *, tmp=row_number() over (partition by ID order by getdate())
 from T
 ) A
where tmp=1

[feixianxxx]

select * from tb a
where 子ID = (
select top 1 子ID from tb
where id=a.id
order by 子ID  
)

[zhengjialon]

用了feixianxxx的，速度还不错，not exists 太慢了，谢各位！