From: Marc Rohloff <Marc.Rohloff@eskom.co.za>
To: pgsql-sql@postgresql.org
Subject: Outer Joins
Date: Wed, 01 Nov 2000 10:02:22 +0200
Message-ID: <s9ffea47.097@eskom.co.za> (raw)
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
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To: pgsql-sql@postgresql.org
Cc: Marc.Rohloff@eskom.co.za
Subject: Re: Outer Joins
In-Reply-To: <s9ffea47.097@eskom.co.za>
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