sql排序分组问题

[fangquan1980]

有以下数据，其中2列：
a b c....
----------------------
1 b1
2 b2
3 b1
4 b3
5 b4
6 b2


要求效果
a b c....
---------------------
1 b1
3 b1
2 b2
6 b2
4 b3
5 b4

即按照b出现的先后顺序排序然后分组

[百年树人]

select a.*
from tb a,
(select b,min(a) as px from tb group by b)b
where a.b=b.b
order by px

[dawugui]

select * from tb order by b , a

[喜-喜]

select * from tb order by b,a

[dawugui]

select m.* from tb m,
(select * from tb t where a = (select min(a) from tb where b = t.b)) n
where m.b = n.b
order by n.a

[dawugui]

create table tb(a int, b varchar(10),c int)
insert into tb values(1 ,'b1',null)
insert into tb values(2 ,'b2',null)
insert into tb values(3 ,'b1',null)
insert into tb values(4 ,'b3',null)
insert into tb values(5 ,'b4',null)
insert into tb values(6 ,'b2',null)
go
select m.* from tb m,
(select * from tb t where a = (select min(a) from tb where b = t.b)) n
where m.b = n.b
order by n.a

drop table tb

/*
a           b          c           
----------- ---------- ----------- 
1           b1         NULL
3           b1         NULL
2           b2         NULL
6           b2         NULL
4           b3         NULL
5           b4         NULL

（所影响的行数为 6 行）
*/