Originally posted by TomazZ
Logically correct, but
select b.id from bx b where not exists (select * from ax a where a.id = b.id)
Even better for this would be

select b.id from bx b where not exists (select 'X' from ax a where a.id = b.id)

But, you know what, there will be N Solution for 1 Question....and i dont want to list all...Its upto the thread starter to dig something from NET or Manuals to find efficient way.

Of course, had he asked for efficient and logically corect ans, then I would bet the above query would out perform rest.

Abhay.