Subject: Re: help with "delete joins"
From: Robert Treat <xzilla@users.sourceforge.net>
To: Josh Berkus <josh@agliodbs.com>,
	Stephan Szabo <sszabo@megazone23.bigpanda.com>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <200306301735.29482.josh@agliodbs.com>
References: <1057011998.24310.348.camel@camel>
	<200306301735.29482.josh@agliodbs.com>
Content-Type: text/plain
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Date: 01 Jul 2003 09:43:07 -0400
Message-Id: <1057066987.24310.383.camel@camel>
Mime-Version: 1.0

On Mon, 2003-06-30 at 20:35, Josh Berkus wrote:
> Robert,
> 
> > delete * from foo where not (foo.a = bar.a and foo.b=bar.b and
> > foo.c=bar.c) ;
> > 
> > so i end up with 
> > 
> > postgres=# select * from foo; 
> >  a | b | c | d 
> > ---+---+---+---
> >  1 | 2 | 4 | A
> >  4 | 5 | 6 | b
> > (2 rows)
> > 
> > but thats not valid sql, is there some way to accomplish this? 
> 
> Um, your example result doesn't match your pseudo-query. 

the end of a long day that started with 4 hours of sleep... no wonder I
couldn't get my head around this one. I actually did want the results of
the psuedo query, not the results I posted :-\

> Assuming that you 
> want to delete everything that DOES match, not everything that DOESN'T, do:
> 
> DELETE FROM foo 
> WHERE EXISTS ( SELECT bar.a FROM bar
> 	WHERE bar.a = foo.a AND bar.b = foo.b
> 		AND bar.c = foo.c );

I was almost there with my original query... a NOT on your/stephan's 
query gets me what I really want. :-)  Thanks guys. 

Robert Treat
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