Hi All, So just as I thought I understood ST_Difference, I'm again confounded with some bizarre behaviour I can't figure out.
I have a bunch of polygons all over the world that I've successfully grouped by country name. So for example, in India I have a single geometry that is a multipolygon, that consists of probably around 3000 random shaped polys in India. That is table A. I took those polygons and buffered them all by some amount. This produced...buffered polygons, as expected. That is table B. What I want to do now is remove the original polygons from the buffered poygons, and keep everything grouped by country, thereby leaving me the bit that I buffered by without the original. ST_Difference...right? Here's what I tried: SELECT A. country_name, ST_Difference(A.buffered_geom, B.buffered_geom) from A,B GROUP by A; What I get as the return value is A. Nothing more, nothing less. Any ideas? Cheers, dylan _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
