Concatenate strings using GROUP BY

Hi,

Let's say we have a query like:

SELECT id, fk, str
FROM foo

... which returns:

id fk str
---------------
1 1 a
2 1 b
3 2 c

Is there a pure SQL way of contactenating str values into a single string,
and get instead:

id fk str
---------------
1 1 a/b
2 12 c

I was thinking of something like:

SELECT id, fk, CONCAT(str || '/')
FROM FOO
GROUP BY fk

Do we have to use PL/PGSQL for that?

Thanks,

----------------------------------
Philippe Lang, Ing. Dipl. EPFL
Attik System
rte de la Fonderie 2
1700 Fribourg
Switzerland
http://www.attiksystem.ch

Tel: +41 (26) 422 13 75
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Email: philippe(dot)lang(at)attiksystem(dot)ch