Subject: Re: How to re-sort a sorted query?
From: Oliver Elphick <olly@lfix.co.uk>
Reply-To: olly@lfix.co.uk
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Yudie <yudie@axiontech.com>, pgsql-sql@postgresql.org
In-Reply-To: <13739.1098827021@sss.pgh.pa.us>
References: <003001c4bb91$4c6647c0$a101a8c0@home.axiontech.com>
	<1098822881.2414.42.camel@linda>  <13739.1098827021@sss.pgh.pa.us>
Content-Type: text/plain
Organization: LFIX Limited
Date: Tue, 26 Oct 2004 22:57:53 +0100
Message-Id: <1098827873.2414.47.camel@linda>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

On Tue, 2004-10-26 at 17:43 -0400, Tom Lane wrote:
> Oliver Elphick <olly@lfix.co.uk> writes:
> > On Tue, 2004-10-26 at 14:23 -0500, Yudie wrote:
> >> Then I do this query to get unique store number and also the cheapest
> >> price from each store:
> >> 
> >> SQL= "Select distinct on (storenumber), itemsku, storenumber,price
> >> from storeproduct where itemsku='10001' 
> >> order by storenumber, price"
> 
> > That won't get you the cheapest price,
> 
> Sure it will.  It's a perfectly good application of DISTINCT ON.
> However, he has to use that particular ORDER BY to get the answers
> he wants.

Ah - because ORDER BY is applied before DISTINCT ON; I hadn't realised
that.

-- 
Oliver Elphick                                          olly@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA  92C8 39E7 280E 3631 3F0E  1EC0 5664 7A2F A543 10EA
                 ========================================
     "Whosoever therefore shall be ashamed of me and of my 
      words in this adulterous and sinful generation; of him
      also shall the Son of man be ashamed, when he cometh 
      in the glory of his Father with the holy angels."     
                                 Mark 8:38