There is no way to visualize a convexhull in qgis 1.8 lisboa? I have tried following views in Postgis 1.5
I was told to use an id column to publish it in Qgis. If you not use an id column, u cannot load it anyway because of an error.
1.
create or replace view con_hull_baeume3(bid) as
select '0', ST_ConvexHull(ST_Collect(geom)) FROM baeume;
2.
create or replace view con_hull_baeume4(bid) as
select bid, ST_ConvexHull(ST_Collect(geom)) FROM baeume group by bid;
but this one make a convexhull on each of the geometrypoints. I mean just use 'select ST_ConvexHull(ST_Collect(geom)) FROM baeume;' works as sql perfectly. But i must define it as a view to load it into a postgis layer of QGIS.