[postgis-users] species diversity query....

[Gilles Bassière]

Hi,

You can't mix aggregate and attribute in the SELECT clause.
In order to build one geometries from a set of geometries, you have
bassically two spatial aggregates : St_Collect() and ST_Union(). Please
refer to the documentation to choose which is more relevant to your case.

Your query would look like:
    SELECT count(the_geom), ST_Union(the_geom) FROM pigs;

The result of the query is a single row with two columns. The first col
hold the number of row where the_geom is not null and the second col is
a multipolygon geometry representing all your "pigs" geometries.

Hope it helps,
Gilles

Horacio Samaniego wrote:
> Hi, 
> I've been trying to devise a way to make this simple query, with no
> success. Any help will be appreciated.
> 
> I have a table with multipoligons and need to generate a unique poligon
> with the count of polys. To be specific, I'm looking to generate a layer
> with species diversity based on the count of individual species
> distribution stored in a table as multipoligons.
> 
> I have been trying
> 
> 
> SELECT count(DISTINCT id),the_geom into BIODIVERSITY FROM pigs WHERE
> the_geom && the_geom GROUP BY the_geom
> 
> 
> however, this obviously doesn't work...
> 
> any hint from experiences queriers would be appreciated!!
> 
> 
> 
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-- 
Gilles Bassiere - MAKINA CORPUS
http://www.makina-corpus.com