SQLServer ntile获取每组前10%的数据

sqlserver2005有关键字ntile(x)和over(partition by.. order by..)子句配合.

比如获取每个表的前10%个字段。
代码如下:
select id , name , colid , rn from (
select * , rn = ntile (10 )
over (partition by id order by colorder )
from syscolumns )t where rn = 1