I clip a polylines vector layer with a polygon vector layer, containing one single polygon. I need my polylines to be clipped at the polygon's boundaries.
CREATE TABLE test AS (SELECT a.gid, st_intersection(a.geom, b.geom) FROM lines a, polygon b WHERE st_intersects(a.geom, b.geom));
I can't visualize the
test table in QGIS because the type of
geom column seems not to be recognized (see image below, which is DB Manager GUI). Thus I tried to specify it within pgAdmin:
ALTER TABLE test ALTER COLUMN geom TYPE geometry(MultiLineString) USING geom::geometry(MultiLineString);
This issues the following error message:
ERROR: Geometry type (LineString) does not match column type (MultiLineString)
I tried to keep the geometry column from the polylines layer together with the
CREATE TABLE test AS (SELECT a.gid, a.geom, st_intersection(a.geom, b.geom) FROM lines a, polygon b WHERE st_intersects(a.geom, b.geom));
This allows to display the table within QGIS but as there are 2 geometry columns produced, the clipping is not displayed and QGIS considers that 2 tables were created.
I need to make a clean clipping of my polylines layer resulting in a new table with a geometry columns having
geometry(MultiLineString) type and displaying well in DB Manager.