On Jul 29, 12:08 am, alvhe...@commandprompt.com (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%40alv...
>
> the text is in spanish but the SQL commands should be trivial to follow.
>
> I think this is a FAQ.
>
> --
> Alvaro Herrera http://www.CommandPrompt.com/
> PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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Appropos, have you had a chance to compare the performance of this
approach and when you use array_to_string( array_accum( $1 ), ' ' )
instead of the text_concat( $1 ) PL/pgSQL based aggregate function?
