Re: [SQL] outer joins strangeness

From: Alex Pilosov <alex(at)pilosoft(dot)com>
To: Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [SQL] outer joins strangeness
Date: 2001-09-24 17:00:23
Message-ID: Pine.BSO.4.10.10109241257190.3287-100000@spider.pilosoft.com
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On Mon, 24 Sep 2001, Stephan Szabo wrote:

> > Postgres should understand that left outer join does not constrict join
> > order...
>
> But it can. If your condition was a joining between the other table
> and the right side of the left outer join, you'd have the same condition
> as a right outer join and the left side. The real condition I think
> is that you can join a non-explicitly joined table to the <x> side of an
> <x> outer join before the outer join but not to the other side.
Yes yes. Maybe I was imprecise. Right join and left join are the same,
only the ordering is different. Lets call the table that will always be
included in a join a "complete" table.

Then, joins should not impose join order on "complete" table. Of course,
joins against 'incomplete' table must be done only after outer join is
done.

Anyone who can actually fix it? :)
-alex

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