Color coding from two data sources

[Mark Leslie]

Don Drake wrote:
> On 10/16/07, Mark Leslie <mark.leslie at lisasoft.com> wrote:
>> Don Drake wrote:
>>> Here's my scenario, I have shapefiles containing polygons of
>> zipcodes.  I
>>> have a table in Postgres that has a zip code with data that I would like
>> to
>>> thematically map.  I am not interested in loading the zipcodes into
>> PostGIS
>>> if I don't have to.  I am using PHP/Mapscript, and I was wondering if
>> there
>>> is a way to merge the Postgres data with the shapefile layer on a map?
>>>
>>> Thanks.
>>>
>>> -Don
>>>
>> That depends what you mean by 'merge'.  If you want to display both in
>> the same layer, you can come close by defining two layers in the same
>> group (see the GROUP item at
>> http://mapserver.gis.umn.edu/docs/reference/mapfile/layer).  If you want
>> to join the two sources together, Jeff has a nice example in the
>> reference docs
>> (
>> http://mapserver.gis.umn.edu/docs/reference/mapfile/join#example-2-join-from-shp-file-to-postgresql-table
>> ).
>> If I've missed the point entirely, then I'll need some more details
>> about what you're trying to end up with.
>>
>>
> 
> Very interesting.  It looks like the second link is close to what I need,
> the first is not what I need.
> 
> The thing is that the postgres table the data is coming out of does not have
> a geometry column, the key is the zipcode.  Furthermore, it will probably
> come from a query, or a view.  I tried using a view with no geometry and
> could not get it to work.  The geometry will come from a shapefile.
> 
> If this would work, could I color code using an expression?  Is there a
> Mapscript alternative?
> 
> Thanks.
> 
> -Don
> 

If there's no geometry in the table, then the join is your only option
AFAIK.  The downside is that joins are only intended for use in queries,
not in styling.  I expect that since you're using MapScript, you could
execute a query to determine membership and dynamically setup the
styling, but that's a reasonably horrible solution.  You'd be better of
using php to connect directly to postgres (http://au2.php.net/pgsql) to
find a zipcodes and set up your classes from that.  Can I ask why you
don't want to load the zipcodes into PostGIS, or extract the table to
shapefile for that matter?  Does the zipcode table change frequently?

-- 
Mark Leslie
Software Architect
LISAsoft Pty Ltd
www.lisasoft.com