Alvaro Herrera wrote:
Raymond C. Rodgers escribió:
The query in which I'm using array_accum() is building a
list of companies and the associated publishers for each. For example:
SELECT c.company_id, c.company_name, array_accum(p.publisher_name) AS
publishers FROM company_table c LEFT JOIN company_publisher_assoc cpa ON
c.company_id = cpa.company_id LEFT JOIN publisher_table p ON
cpa.publisher_id = p.publisher_id GROUP BY c.company_id, c.company_name
ORDER BY company_name
(This query isn't direct out of my code, and thus may have errors, but
it should convey the idea of what I'm trying to accomplish.)
The result is that I should have a single row containing the company_id,
company_name, and publishers' names if any.
In order to do this you can use a custom aggregate function to
concatenate the texts. I have described this previously here:
http://archives.postgresql.org/message-id/20080327234052.GZ8764%40alvh.no-ip.org
the text is in spanish but the SQL commands should be trivial to follow.
I think this is a FAQ.
Thanks for the link, and the SQL is simple enough to follow. I'll give it a whirl. It would certainly be useful to have that SQL posted as a comment on the PostgreSQL documentation page I referenced earlier; maybe it could stop being a FAQ, and end up a FFA (Frequently Found Answer) :-)
Thanks again,
Raymond