排序精典，不得不看~

declare @t table(id int,Uid int,Str varchar(4))
insert into @t select 1,5,'aaa'
insert into @t select 2,5,'bbb'
insert into @t select 3,5,'ccc'
insert into @t select 4,6,'ddd'
insert into @t select 5,6,'eee'
insert into @t select 6,8,'ggg'
insert into @t select 7,8,'ttt'
insert into @t select 8,2,'uuu'
insert into @t select 9,2,'hhh'

select a.* from @t a order by (select count(*) from @t where Uid=a.Uid and id<=a.id),uid

/*
id          Uid         Str 
----------- ----------- ----
8           2           uuu
1           5           aaa
4           6           ddd
6           8           ggg
9           2           hhh
2           5           bbb
5           6           eee
7           8           ttt
3           5           ccc
*/