Jonathan Moore <moore@discern.com> writes:
> I now under stand that my join was rong but none of the seguestions are
> the optimal solution to the problime. You can make this order n if you
> try. The trick is to use a mearg join using sorted list of the unique
> keys in each colum join. The question you are asking is what left hand
> entrys do not exist on the right.
In that case maybe what you are after is
select a.* from a left join b on (a.left = b.right) where b.right is null;
which is a pretty grotty hack using the outer-join rules, but should
work efficiently.
regards, tom lane