[postgis-users] count points for every polygon

[Astrid Emde]

Hello Alexander,

have a look at

http://postgis.org/documentation/manual-1.4/ch07.html

and try

* ST_NumPoints - to get the Number of Points of a Linestring
* ST_ExteriorRing - to get a linestring from your Polygon
* if you have MULTIPOLYGONS you may need ST_NumGeometries, ST_GeometryN

Best regards

Astrid

On Tue, December 1, 2009 8:58 am, Alexander Strunck wrote:
> hello
>
> i am new to postgis and sql. my problem is that i want to count the
> points that are in every polygon. the polygon table contains gid, id,
> geom. the points table contains id, geom. i found in the internet this sql
>
>> UPDATE polygon SET number_points = foo.count
>> FROM (
>> SELECT polygon.name, count(point.gid) AS count
>> FROM point, polygon
>> WHERE ST_Contains(polygon.the_geom, point.the_geom)
>> GROUP BY polygon.name
>> ) AS foo
>> WHERE polygon.name = foo.name;
>>
>
> but it don´t seem to work for me.
>
> Has anyone an idea how to make this work??
>
>
> thx
>
> alex --
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