Message-ID: <4B32DB14.6080308@postnewspapers.com.au>
Date: Thu, 24 Dec 2009 11:08:04 +0800
From: Craig Ringer <craig@postnewspapers.com.au>
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To: Rosser Schwarz <rosser.schwarz@gmail.com>
CC: Bryce Nesbitt <bryce2@obviously.com>, sql pgsql <pgsql-sql@postgresql.org>
Subject: Re: Using || operator to fold multiple columns into one
References: <4B31D619.1090706@obviously.com>	
	<4B31D86D.9030000@postnewspapers.com.au>
	<37d451f70912231304i3515e575x69b31638962739a6@mail.gmail.com>
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On 24/12/2009 5:04 AM, Rosser Schwarz wrote:
> On Wed, Dec 23, 2009 at 1:44 AM, Craig Ringer
> <craig@postnewspapers.com.au>  wrote:
>
>> SELECT COALESCE( t_number::text, t:string::text, t_date::text, t_boolean::text) AS value;
>
> Your invocation of COALESCE is incorrect -- it is n-ary, but it
> returns its first non-NULL argument.

Yes. That was the point.

I think we're assuming the OP wants different things. You're assuming 
they're trying to concatenate all fields, where more than one field in a 
given record may be non-null. I'm assuming that all but one field in 
each record will be null, and they want to show the "value" of the 
record - in other words, they're using the record as a sort of union 
type. It looks like that from the example they gave.

--
Craig Ringer