Thread: combine multiple row values in to one row
Hi;
I'm looking for a way to do this:
# \d tbl
Table "public.tbl"
Column | Type | Modifiers
--------+---------+-----------
idn | integer |
code | text |
# SELECT * FROM tbl;
idn | code
-----+------
1 | A
2 | B
2 | C
3 | A
3 | C
3 | E
(6 rows)
# select idn, magic() as codes FROM tbl;
idn | codes
-----+------
1 | A
2 | B, C
3 | A, C, E
(3 rows)
Right now, I use plpgsql functions, but each time I do it
I have to rewrite the function to customize it.
Is there a generic way to do this? An aggregate maybe?
Thanks for any help.
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On Tue, 7 Jul 2009 01:59:35 +0430 Lee Harr <missive@hotmail.com> wrote: > > Hi; > > I'm looking for a way to do this: > # select idn, magic() as codes FROM tbl; > idn | codes > -----+------ > 1 | A > 2 | B, C > 3 | A, C, E > (3 rows) > > > Right now, I use plpgsql functions, but each time I do it > I have to rewrite the function to customize it. > > Is there a generic way to do this? An aggregate maybe? array_accum http://www.postgresql.org/docs/8.2/static/xaggr.html ? -- Ivan Sergio Borgonovo http://www.webthatworks.it
Try this.
select idn,
array_to_string(array(select code from tbl t2 where
t2.idn = t1.idn order by code), ', ') as codes
from tbl t1
group by idn
order by idn
Matthew Hartman
Programmer/Analyst
Information Management, ICP
Kingston General Hospital
(613) 549-6666 x4294
> -----Original Message-----
> From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-
> owner@postgresql.org] On Behalf Of Lee Harr
> Sent: Monday, July 06, 2009 5:30 PM
> To: pgsql-general@postgresql.org
> Subject: [GENERAL] combine multiple row values in to one row
>
>
> Hi;
>
> I'm looking for a way to do this:
>
>
> # \d tbl
> Table "public.tbl"
> Column | Type | Modifiers
> --------+---------+-----------
> idn | integer |
> code | text |
> # SELECT * FROM tbl;
> idn | code
> -----+------
> 1 | A
> 2 | B
> 2 | C
> 3 | A
> 3 | C
> 3 | E
> (6 rows)
> # select idn, magic() as codes FROM tbl;
> idn | codes
> -----+------
> 1 | A
> 2 | B, C
> 3 | A, C, E
> (3 rows)
>
>
> Right now, I use plpgsql functions, but each time I do it
> I have to rewrite the function to customize it.
>
> Is there a generic way to do this? An aggregate maybe?
>
>
> Thanks for any help.
>
>
> _________________________________________________________________
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.now.
On Tue, Jul 07, 2009 at 01:59:35AM +0430, Lee Harr wrote: > > Hi; > > I'm looking for a way to do this: > > > # \d tbl > Table "public.tbl" > Column | Type | Modifiers > --------+---------+----------- > idn | integer | > code | text | > # SELECT * FROM tbl; > idn | code > -----+------ > 1 | A > 2 | B > 2 | C > 3 | A > 3 | C > 3 | E > (6 rows) > # select idn, magic() as codes FROM tbl; > idn | codes > -----+------ > 1 | A > 2 | B, C > 3 | A, C, E > (3 rows) > > > Right now, I use plpgsql functions, but each time I do it > I have to rewrite the function to customize it. > > Is there a generic way to do this? An aggregate maybe? The aggregate is called array_agg() and it's in 8.4. You can then wrap array_to_string() around it and get pretty formatting, as in: SELECT idn, array_to_string(array_agg(code),', ') AS codes FROM tbl; If you're not on 8.4 yet, you can create a similar aggregate with CREATE AGGREGATE. Cheers, David. -- David Fetter <david@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fetter@gmail.com Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate
On Tue, Jul 07, 2009 at 08:40:06AM -0700, David Fetter wrote:
> On Tue, Jul 07, 2009 at 01:59:35AM +0430, Lee Harr wrote:
> >
> > Is there a generic way to do this? An aggregate maybe?
>
> The aggregate is called array_agg() and it's in 8.4. You can then
> wrap array_to_string() around it and get pretty formatting, as in:
>
> SELECT idn, array_to_string(array_agg(code),', ') AS codes FROM tbl;
Oops. That should read:
SELECT
idn,
array_to_string(array_agg(code),', ') AS codes
FROM tbl
GROUP BY idn; /* gotta group by :) */
Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david.fetter@gmail.com
Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate