To: mailreg@numerixtechnology.de
Cc: Greg Stark <gsstark@mit.edu>, pgsql-sql@postgresql.org
Subject: Re: ORDER BY and NULLs 
In-reply-to: <414DEA7F.6050100@numerixtechnology.de> 
References: <011d01c49e5b$c88fdb20$2766f30a@development.greatgulfhomes.com>
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	<414DB594.5000300@numerixtechnology.de>
	<19733.1095613137@sss.pgh.pa.us>
	<414DBF6D.8040500@numerixtechnology.de>
	<87zn3mjeaw.fsf@stark.xeocode.com>
	<414DEA7F.6050100@numerixtechnology.de>
Comments: In-reply-to T E Schmitz <mailreg@numerixtechnology.de>
	message dated "Sun, 19 Sep 2004 21:22:23 +0100"
Date: Sun, 19 Sep 2004 16:30:29 -0400
Message-ID: <21812.1095625829@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

T E Schmitz <mailreg@numerixtechnology.de> writes:
> Greg Stark wrote:
>> Which book is it?

> PostgreSQL by Korry Douglas + Susan Douglas, ISBN 0-7357-1257-3; Feb 2003

Hmm, I've heard of that book but never seen it.  The authors are not
participants in the PG community --- AFAICT neither of them have ever
posted anything in the mailing lists.

> The paragraph continues:
> "If the SELECT command included the clause WHERE phone NOT NULL, 
> PostgreSQL could use the index to satisfy the ORDER BY clause.
> An index that covers optional (NOT NULL) columns will not be used to 
> speed table joins either."

My goodness, it seems to be a veritable fount of misinformation :-(

I wonder how much of this is stuff that is true for Oracle and they just
assumed it carried over?

			regards, tom lane