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From: Richard Huxton <dev@archonet.com>
Organization: Archonet Ltd
To: Marcus Claesson <marcus.claesson@angiogenetics.se>,
	pgsql-sql@postgresql.org
Subject: Re: How do I concatenate row-wise instead of column-wise?
Date: Tue, 16 Jul 2002 10:15:51 +0100
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On Tuesday 16 Jul 2002 9:09 am, Marcus Claesson wrote:
> I have a table like this:
> SELECT * FROM old_tab;
> id    |    descr
> -------------------
> 3    |    ddd
> 3    |    ddd
> 3    |    eee
> 3    |    fff

> SELECT * FROM new_tab;
> id    |    descr
> --------------------------
> 1    |    aaa;bbb
> 2    |    ccc;bbb
> 3    |    ddd;eee;fff
> 4    |    bbb

You'll want to write your own aggregate function - something like max() whi=
ch=20
will work over a range of values. This is easier than you might think.

The only thing to be careful of is that order isn't guaranteed, so by defau=
lt=20
you could have "ddd;eee;fff" or "fff;ddd;eee" etc.

Go to techdocs.postgresql.org and check the "Postgresql Cookbook" courtesy =
of=20
Roberto Mello and also the "Postgresql Notes" by me. Also check the online=
=20
manual and the mailing archives (try searching on "aggregate" and "catenate=
"=20
or "concat").

HTH

- Richard Huxton