To: Philip Warner <pjw@rhyme.com.au>
cc: Carolyn Lu Wong <carolyn@kss.net.au>,
	"pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
Subject: Re: SQL question 
In-reply-to: <3.0.5.32.20000717141152.022dd100@mail.rhyme.com.au> 
References: <3.0.5.32.20000717121856.022cd100@mail.rhyme.com.au>
	<3.0.5.32.20000717141152.022dd100@mail.rhyme.com.au>
Comments: In-reply-to Philip Warner <pjw@rhyme.com.au>
	message dated "Mon, 17 Jul 2000 14:11:52 +1000"
Date: Mon, 17 Jul 2000 01:48:48 -0400
Message-ID: <28464.963812928@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Philip Warner <pjw@rhyme.com.au> writes:
> Another alternative would be to define a 'coalesce' function (I don't think
> PG has one), which takes an arbitrary number of arguments and returns the
> first non-null one.

We surely do have that!  It even works pretty well in 7.0 ;-)
(I think there were still some bugs lurking in 6.5.)

The immediate cause of this gripe was discussed just a day or so ago
on one or another of the pgsql lists.  The timestamp-to-date conversion
routine has this weird idea that it should kick out an error instead
of returning NULL when presented with a NULL timestamp.  That's a bug
IMHO, and I've already changed the code in current sources.

COALESCE would be a good workaround if you don't want to patch your
local copy of 7.0.*.

			regards, tom lane