Hi, > SELECT > ST_Difference(ST_Union(the_geom), (SELECT the_geom FROM squares WHERE > id='S')) > FROM squares > [...] > Does this return a multipolyon or a single polygon?
I think it depends on whether or not the result is presentable as a single polygon. I had a test case which consisted of disjoint squares which touch each other - in this case the upper query resulted in a single polygon. > I didn't state > this originally, but I have disjointed squares. So if you look at a > grid : > ABCDEF > OPQRST > UVWXYZ > I might have ABCEFOQUVW > ABC EF > O Q > UVW > So I would want one polygon with ABCQWVU and one with EF As far as I know, you may want to produce a multi-polygon M and then use generate_series [1] and ST_GeometryN [2] for retrieving one row for each single-polygon in M - I'm not quite sure on how to do that syntactically, but there is an example in [2], which may help you out. Best regards, Andreas [1] http://www.postgresql.org/docs/8.4/interactive/functions-srf.html [2] http://postgis.refractions.net/docs/ST_GeometryN.html _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
