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怎样一次性删除所有成对的相反数？
表1如下：
id t1 t2
1 a 3
2 b 12
3 a -3
4 a 3
5 a 33
6 b 12
7 b 11
8 c 9
9 c -9
我想把所有的负数及与每个负数相反的一个正数删除，达到以下效果：
id t1 t2
2 b 12
4 a 3
5 a 33
6 b 12
7 b 11
请问用SQL怎么解决？
id t1 t2
1 a 3
2 b 12
3 a -3
4 a 3
5 a 33
6 b 12
7 b 11
8 c 9
9 c -9
我想把所有的负数及与每个负数相反的一个正数删除，达到以下效果：
id t1 t2
2 b 12
4 a 3
5 a 33
6 b 12
7 b 11
请问用SQL怎么解决？
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-狙击手- 2006-01-19
强
wuaza 2006-01-19
子陌兄出手果然厉害，请问你的QQ是多少，非常希望结交你这样的一流高手
子陌红尘 2006-01-19
declare @t table(id int,t1 char(1),t2 int)
insert into @t select 1,'a',3
insert into @t select 2,'b',12
insert into @t select 3,'a',-3
insert into @t select 4,'a',3
insert into @t select 5,'a',33
insert into @t select 6,'b',12
insert into @t select 7,'b',11
insert into @t select 8,'c', 9
insert into @t select 9,'c',-9
delete a from @t a
where
(select count(*) from @t where id<=a.id and t1=a.t1 and t2=a.t2)<=
(select count(*) from @t where t1=a.t1 and t2=-a.t2)
select * from @t
/*
id t1 t2
---- ---- ----
2 b 12
4 a 3
5 a 33
6 b 12
7 b 11
*/
insert into @t select 1,'a',3
insert into @t select 2,'b',12
insert into @t select 3,'a',-3
insert into @t select 4,'a',3
insert into @t select 5,'a',33
insert into @t select 6,'b',12
insert into @t select 7,'b',11
insert into @t select 8,'c', 9
insert into @t select 9,'c',-9
delete a from @t a
where
(select count(*) from @t where id<=a.id and t1=a.t1 and t2=a.t2)<=
(select count(*) from @t where t1=a.t1 and t2=-a.t2)
select * from @t
/*
id t1 t2
---- ---- ----
2 b 12
4 a 3
5 a 33
6 b 12
7 b 11
*/