Regina,
I think I spoke too soon. On closer inspection of the results it looks
like the query is returning all the points in the points table.
select a.file, a.id, a.name
from points a LEFT JOIN polygons b
ON (a.the_geom && b.the_geom
and distance(a.the_geom, b.the_geom) = 0.0)
where b.the_geom IS NULL
I think this has a logic issue, IF b.the_geom is NULL then the ON clause
must also be NULL. Does that work?
I also tried this query, which returned no points:
select file, id, name
from points
where distance(the_geom, (select collect(the_geom) from polygons)) > 0.0';
Any thoughts why this does not appear to work?
I'm going to try your other query and see if I get different results
with that.
Thanks,
-Steve
Obe, Regina wrote:
SELECT a.*
FROM point a LEFT JOIN polygons b
ON (a.the_geom && b.the_geom
and ST_distance(a.the_geom, b.the_geom) = 0.0)
WHERE b.the_geom IS NULL
or
SELECT a.*
FROM point a LEFT JOIN polygons b
ON ST_Within(a.the_geom, b.the_geom)
WHERE b.the_geom IS NULL
I think the second one should be more efficient, but I haven't done any
benchmarks.
Hope that helps,
Regina
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Stephen Woodbridge
Sent: Wednesday, January 23, 2008 10:27 PM
To: PostGIS Users Discussion
Subject: [postgis-users] Spatial query Help: points not in set of
polygons
Hi all,
I'm drawing a blank on setting up a query for this.
I have a tables points and a table of polygons. I need to find all the
points that are not in any of the polygons.
select a.*
from points a, polygons b
where a.the_geom && b.the_geom
and distance(a.the_geom, b.the_geom) > 0.0;
The problem with this is that if a point is in polygon A it will have a
distance to polygon B, so this in no good.
I thought of doing something like:
select * from points
where distance(the_geom, union((select the_geom from polygons))) >
0.0;
or
select * from points
where distance(the_geom, collect((select the_geom from polygons))) >
0.0;
So is there a better way to do this. Seems like there should be. If not
which of these would you suggest.
Thanks,
-Steve
_______________________________________________
postgis-users mailing list
[email protected]
http://postgis.refractions.net/mailman/listinfo/postgis-users
-----------------------------------------
The substance of this message, including any attachments, may be
confidential, legally privileged and/or exempt from disclosure
pursuant to Massachusetts law. It is intended
solely for the addressee. If you received this in error, please
contact the sender and delete the material from any computer.
_______________________________________________
postgis-users mailing list
[email protected]
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________
postgis-users mailing list
[email protected]
http://postgis.refractions.net/mailman/listinfo/postgis-users
