select 'a' as c,1 as n
into #t
union all select 'a',2
union all select 'b',3
union all select 'c',1
union all select 'd',2
union all select 'e',1
union all select 'e',2
union all select 'g',3
/* comment this line with "--" to add additional testdata below
union all select 'x',6
union all select 'x',44
union all select 'x',7
union all select 'y',6
union all select 'y',44
union all select 'y',7
--*/


select
	t1.c as c1
	,t2.c as c2
from
	#t t1 join #t t2
		on t1.c <> t2.c
where
	t1.n = t2.n
group by
	t1.c
	,t2.c
having
	count(*) = (select count(*) from #t t3 where t1.c = t3.c group by t3.c)
	and
	count(*) = (select count(*) from #t t3 where t2.c = t3.c group by t3.c)
	--and count(*) >= 1 -- #of matching records per group


drop table #t