To: Greg Stark <gsstark@mit.edu>
Cc: Stephan Szabo <sszabo@megazone23.bigpanda.com>,
	"Correia,     Carla" <Carla.Correia@logicacmg.com>,
	"'pgsql-sql@postgresql.org'" <pgsql-sql@postgresql.org>
Subject: Re: Complex outer joins? 
In-reply-to: <878yv1l981.fsf@stark.dyndns.tv> 
References: <20030326145855.J66362-100000@megazone23.bigpanda.com>
	<878yv1l981.fsf@stark.dyndns.tv>
Comments: In-reply-to Greg Stark <gsstark@mit.edu>
	message dated "26 Mar 2003 23:33:18 -0500"
Date: Thu, 27 Mar 2003 01:18:19 -0500
Message-ID: <9388.1048745899@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Greg Stark <gsstark@mit.edu> writes:
> Yeah, that's not a particularly enlightening case because if you convert the
> right joins to left joins you see that these aren't actually similar queries
> at all.

> the first is 
>  "C left join (G left join L)" 
> and the second is
>  "G left join (C left join L)"

> They only look similar superficially when written using right joins but
> they're actually totally different structures.

Yup, you're quite right.  What's bothering me is that AFAICS they are
extremely similar in the Oracle notation too: put the (*) on the other
side of one of the equality clauses, and you convert one case to the
other.  So how can you assert that Oracle's notation is not sensitive
to join order?

			regards, tom lane