--？？
Select * 
from #t
where [a]!=[B]

------解决方案--------------------
SQL code

declare @tablename table (A varchar(4),B varchar(4))
insert into @tablename
select '1111','1111' union all
select '1111','AAAA' union all
select '1111','1111' union all
select '2222','2222' union all
select '2222','2222' union all
select '2222','2222' union all
select '3333','3333' union all
select '444','444'

select a.* from @tablename a right join @tablename b
on a.A=b.A where b.A<>b.B
/*
A    B
---- ----
1111 1111
1111 AAAA
1111 1111
*/

------解决方案--------------------
SQL code
select * from 
ta where a!=b

------解决方案--------------------
SQL code
----创建测试数据
if object_id('ta')  is not null  drop table ta
create table ta (A varchar(20),B varchar(20))
insert into ta 
select '1111','1111' union all
select '1111','AAAA' union all
select '1111','1111' union all
select '2222','2222' union all
select '2222','2222' union all
select '2222','2222' union all
select '3333','3333' union all
select '444','444'
---查询
(select a ,b from ta)
union 
(select a,b from ta)

------解决方案--------------------
SQL code

declare @tablename table (A varchar(4),B varchar(4))
insert into @tablename
select '1111','1111' union all
select '1111','AAAA' union all
select '1111','1111' union all
select '2222','2222' union all
select '2222','2222' union all
select '2222','2222' union all
select '3333','3333' union all
select '444','444' union all
select '5555','bbb' union all
select '5555','bbb'

select a.* from @tablename a right join @tablename b
on a.A=b.A left join
(select count(distinct B) as c1,A from @tablename group by A ) c
on b.A=c.A where c.c1>1 and b.A<>b.B

/*
A    B
---- ----
1111 1111
1111 AAAA
1111 1111
*/