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Re: Outer joins and equivalence

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Matthew Wakeling <matthew(at)flymine(dot)org>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Outer joins and equivalence
Date: 2008-05-28 13:39:10
Message-ID: 1211981950.4489.473.camel@ebony.site (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
On Wed, 2008-05-28 at 11:45 +0100, Matthew Wakeling wrote:
> On Tue, 27 May 2008, Simon Riggs wrote:
> > I do recognise that we would *not* be able to deduce this form of SQL
> >
> > A JOIN B ON (a.id = c.id) LEFT JOIN C ON (b.id = c.id)
> 
> Surely that would not be valid SQL?

You are right, but my point was about inferences during SQL planning,
not about initial analysis of the statement.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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