From: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-sql@postgresql.org
Subject: Re: How to collect text-fields from multiple rows ?
Date: Sat, 16 Oct 2010 09:23:03 +0200
Message-ID: <i9bjsn$l4b$1@dough.gmane.org> (raw)
In-Reply-To: <4CB91AAE.6030602@gmx.net>
References: <4CB91AAE.6030602@gmx.net>
Andreas wrote on 16.10.2010 05:23:
> Hi,
>
> how can I collect text-fields from multiple rows into one output row?
> I'd like to do an equivalent to the aggregate function SUM() only for text.
>
> The input is a select that shows among other things a numerical column where I would like to group by.
> The text column of all rows in a group should get concatenated into 1 text devided by a '\n'.
>
> Even better would be if I could add a second text colum per line as topic.
>
> Input e.g.
> select group_nr::integer, memo::text, topic::text ...
>
> 1, 'bla ', 'weather'
> 2, 'yada..', 'weather'
> 2, 'talk talk..', 'cooking'
> 2, 'words words, ...', 'poetry'
> 3, ....
>
> Output:
>
> 1, 'weather\nbla...'
> 2, 'weather\nyada..\ncooking\ntalk talk..\npoetry\nwords words, ...'
>
If you are on 9.0:
SELECT group_nr, string_agg(memo||'--'||topic, '--')
FROM the_table_with_no_name
GROUP BY group_nr;
On 8.x you need to user array_agg()
SELECT group_nr, array_to_string(array_agg(memo||'--'||topic),'--')
FROM the_table_with_no_name
GROUP BY group_nr;
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: spam_eater@gmx.net
Subject: Re: How to collect text-fields from multiple rows ?
In-Reply-To: <i9bjsn$l4b$1@dough.gmane.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox