I've been looking at the open-source databases for a project I am working on and while reading about Postgres I saw
thatthey do not support outer joins yet. I was intrigued by their solution of using a union query.
Something Like:
select a.col1, b.col2 from a,b where a.col1 = b.col2
union
select a.col1, NULL from a where a.col1 not in (select b.col2 from b)
But I was wondering if the following would work (it does in some other databases)
select a.col1, b.col2 from a,b
where a.col1 = b.col2 or b.col2 is null
or maybe even
select a.col1, b.col2 from a,b
where a.col1 = b.col2 or a.col1 not in (select b.col2 from b)
These would seem to be far more efficient than a union query
(I would try this but I don't have a Unix box at the moment to install PostgreSQL on!)
Marc Rohloff