I've two geometry table inside my DB:
- buffer: id INTEGER SERIAL PRIMARY KEY, geom POLYGON
- polygons: geom MULTIPOLYGON
I need have the intersection between buffer and polygons and I will do this using this TRIGGER:
CREATE OR REPLACE FUNCTION intersection_function() RETURNS TRIGGER AS $$ BEGIN SELECT a.id as idb, ST_Intersection(NEW.a.geom, NEW.b.geom) as geom FROM buffer as a, polygons as b WHERE ST_Intersects(a.geom, b.geom); RETURN NEW; END; $$ LANGUAGE 'plpgsql'; CREATE TRIGGER intersection_trigger AFTER INSERT OR UPDATE ON test_intersection FOR EACH ROW EXECUTE PROCEDURE intersection_function();
Table test_intersection has: id INTEGER SERIAL PRIMARY KEY, idb INTEGER and geom MULTIPOLYGON.
When I draw a polygon inside buffer table I expect to have the result of intersection inside test_intersection but that table is always empty.
It is my first trigger, what I've wrong?