有点难道的sql语句，请大家来试下！
declare   @test   table(id   int,   title   varchar(20))
declare   @sub   table(id   int,test_id   int,   subtitle   varchar(20))
insert   into   @test   values(1, 'firstTitle ')
insert   into   @sub   values(1,1, 'firstSubTitle ')
insert   into   @sub   values(2,1, 'secondSubTitle ')
insert   into   @test   values(2, 'secondTitle ')
insert   into   @sub   values(3,2, 'secondfirstSubTitle ')
insert   into   @sub   values(4,2, 'secondsecondSubTitle ')
select   a.*,b.id   as   sub_id,b.subtitle  
from   @test   a,@sub   b
where   a.id=b.test_id
这样得到的结果是：
1 firstTitle 1 firstSubTitle
1 firstTitle 2 secondSubTitle
2 secondTitle 3 secondfirstSubTitle
2 secondTitle 4 secondsecondSubTitle
但是我想要的结果却是：
1 firstTitle 2 secondSubTitle
2 secondTitle 4 secondsecondSubTitle
请问sql语句该怎么写？

------解决方案--------------------
select a.*,b.id as sub_id,b.subtitle
from @test a,@sub b
where a.id=b.test_id
and not exists(select 1 from @sub where b.test_id = test_id and len(b.subtitle) < len(subtitle))
------解决方案--------------------
select m.* from
(
select a.*,b.id as sub_id,b.subtitle
from @test a,@sub b
where a.id=b.test_id
) m,
(
select n.id , max(sub_id) sub_id from
(
select a.*,b.id as sub_id,b.subtitle
from @test a,@sub b
where a.id=b.test_id
) n group by id
) p
where m.id = p.id and m.sub_id = p.sub_id
------解决方案--------------------
如果是取最后的，加上
and not exists(select 0 from @sub c where c.test_id=b.test_id and c.id <b.id)
------解决方案--------------------
select a.*,d.id as sub_id,d.subtitle from test a,
(
select b.* from sub b,
(
select test_id , max(id) id from sub group by test_id
) c
where b.test_id = c.test.id and b.id = c.id
) d
where a.id = d.test_id