[postgis-users] One-to-many join

[John Morgan]

Andy,
I got this working.  You tip to use the aggregate function was what I was
looking for.  However, as I am only on version 8 postgresql I ended up
using   array_to_string but it worked just the same.

Cheers and thanks,
Derek

On Mon, Jan 30, 2012 at 10:54 PM, Andy Colson <andy at squeakycode.net> wrote:

> On 01/30/2012 09:00 PM, John Morgan wrote:
>
>> Hello,
>> I am attempting to get a one (polys) to many (table) to load postgis data
>> within a mapserver wms.  I have the following defined in the .map file.
>>
>> DATA "the_geom FROM (SELECT polys.gid AS gid, polys.the_g
>> eom AS the_geom, table.pt_id AS pt_id, table.agent AS agent FROM polys
>> RIGHT OUTER JOIN
>> table ON polys.pt_id = table.pt_id) as new_table USING UNIQUE gid USING
>> SRID=4326"
>>
>> It does load, the layer, however, it doesn't seem to be performing the
>> one-to-many for the attributes on identify.  Thanks for any feedback.
>>
>> Cheers,
>> Derek
>>
>>
> But.... that would return the exact same the_geom multiple times.  Which
> would draw all on top of each other (including the label?), so it would
> only look like one.
>
> What is it you are trying to do?  Looks like get all the agent's to
> display for one area?
> If you are using PG 9, how about something like:
>
> DATA "the_geom FROM (SELECT polys.gid AS gid, polys.the_geom AS the_geom,
> (select string_agg(agent, E'\n') from table where polys.pt_id =
> table.pt_id) AS agents FROM polys) as new_table USING UNIQUE gid USING
> SRID=4326"
>
> That'll return all the agents in a single string separated by carage
> return.
>
> -Andy
>
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