From: | Richard Huxton <dev(at)archonet(dot)com> |
---|---|
To: | Kai Hessing <kai(dot)hessing(at)hobsons(dot)de> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Advanced SELECT |
Date: | 2005-02-24 08:21:58 |
Message-ID: | 421D8EA6.7020107@archonet.com |
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Lists: | pgsql-general pgsql-sql |
Kai Hessing wrote:
>
> The normal clause would look like:
>
> SELECT c.companyname, s.sectorname FROM company c, sector s,
> company_sector cs WHERE cs.cid = c.cid AND cs.sid = s.sid ORDER BY
> c.companyname;
> c.companyname | ??? (sectors)
> ---------------+------------------------
> company1 | sectora, sectorb
> company2 | sectora, sectorb, sectorc
> company3 | sectora
> company4 | sectorc
>
Search the mailing-list archives for "custom aggregate concat" and
you'll quickly find an example of how to write your own custom aggregate
(like SUM()).
Warning - I don't think you can guarantee the order of elements in the
aggregated sectors.
--
Richard Huxton
Archonet Ltd
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