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Date: Wed, 01 Nov 2000 10:02:22 +0200
From: "Marc Rohloff" <Marc.Rohloff@eskom.co.za>
To: <pgsql-sql@postgresql.org>
Subject: Outer Joins
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I've been looking at the open-source databases for a project I am working on and while reading about Postgres I saw that they 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