Date: Mon, 12 Sep 2005 17:03:23 -0600
From: Michael Fuhr <mike@fuhr.org>
To: gherzig@fmed.uba.ar
Cc: pgsql-sql@postgresql.org
Subject: Re: refer a column as a varible name?
Message-ID: <20050912230323.GA63469@winnie.fuhr.org>
References: <56093.157.92.152.53.1126538482.squirrel@webmail.fmed.uba.ar>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <56093.157.92.152.53.1126538482.squirrel@webmail.fmed.uba.ar>

On Mon, Sep 12, 2005 at 12:21:22PM -0300, gherzig@fmed.uba.ar wrote:
> suppose the
> 
> type mycolumn as (field1, varchar, field2 varchar)
> and
> 
> field_name = ''field1''
> 
> and returnValue declared as mycolumn
> ...
> can i say returnValue.$field_name = ''ok''?

To achieve this in PL/pgSQL you'll need to use a conditional statement
(IF field_name = 'field1' THEN ...).  I'm not sure if a solution
involving EXECUTE is possible; if so then it's probably non-obvious.

What version of PostgreSQL are you using, and do you have a requirement
to use PL/pgSQL?  In 8.0 PL/Perl can return composite types and such
an assignment would be trivial:

CREATE TYPE mycolumn AS (field1 varchar, field2 varchar);

CREATE FUNCTION foo(varchar) RETURNS mycolumn AS $$
my $field_name = $_[0];
my $returnValue = {$field_name => "ok"};
return $returnValue;
$$ LANGUAGE plperl IMMUTABLE STRICT;

SELECT * FROM foo('field1');
 field1 | field2 
--------+--------
 ok     | 
(1 row)

SELECT * FROM foo('field2');
 field1 | field2 
--------+--------
        | ok
(1 row)

-- 
Michael Fuhr