set nocount on

declare @t1 table (f1 int, f2 int)
declare @t2 table (f1 int, f2 int)

insert @t1 values( 10 , 10 )
insert @t1 values( 20 , 20 )
insert @t1 values( 30 , 30 )

insert @t2 values( 11 , 10 )
insert @t2 values( 20 , 20 )
insert @t2 values( 30 , 30 )

select * from @t1 t1 left join @t2 t2 on t1.f1 = t2.f1 and t1.f2 = t2.f2 where t2.f1 is null and t2.f2 is null
 union all
select * from @t2 t2 left join @t1 t1 on t1.f1 = t2.f1 and t1.f2 = t2.f2 where t1.f1 is null and t1.f2 is null 

способ получше:

select coalesce(t1.f1,t2.f1) f1, coalesce(t1.f2,t2.f2) f2
from t1
full join t2
on t1.f1=t2.f1 and t1.f2=t2.f2 
where t1.f1 is null or t2.f1 is null
go