Hi Brian, > I have squares. A lot of squares. Thousands of squares. I would > love > to combine them into one or more larger polygons. But, they must > valid > polygons, non-reentrant. For example. if you have a 3x3 grid of > squares, > ABC > RST > XYZ > and I want to combine all but the center, I would need either 2 > polygons > (something like ABC and RXYZT), or one polygon with an inner ring.
Assuming there is a table 'squares' containing a geometry type 'the_geom', this one produces a polygon having an inner ring: SELECT ST_Difference(ST_Union(the_geom), (SELECT the_geom FROM squares WHERE id='S')) FROM squares Best Regards, Andreas _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
