To: johnf <jfabiani@yolo.com>
cc: pgsql-sql@postgresql.org
Subject: Re: setting the where clause 
In-reply-to: <200906100519.34171.jfabiani@yolo.com> 
References: <200906100519.34171.jfabiani@yolo.com>
Comments: In-reply-to johnf <jfabiani@yolo.com>
	message dated "Wed, 10 Jun 2009 05:19:34 -0700"
Date: Wed, 10 Jun 2009 10:19:14 -0400
Message-ID: <347.1244643554@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

johnf <jfabiani@yolo.com> writes:
> I'm am programming in python using the Dabo modules.  www.dabodev.com if your 
> interested.  Dabo is a framework that provides an easy way to build desktop 
> app's.  To clear a data entry form. I have been setting the where clause 
> to "where 1=0".  This of course retrieves 0 records and my form will display 
> nothing.  It has been suggested that it might be better to set the where 
> clause to a primary key value that does not exist in the table  "where PK 
> = -9999999".   

Whoever said that doesn't know what they're talking about.  It's not
faster (because it forces an actual index probe to happen) and it's not
safer (what if one day that PK value exists?).

I'd personally go with "where false"; why not say what you mean rather
than forcing humans and computers to deduce that the condition is
constant false?

			regards, tom lane