canvas = qgis.utils.iface.mapCanvas()
    csql='ST_Intersects("p1".geom, "p2".geom)'
    uri = QgsDataSourceURI()
    uri.setConnection("localhost", "5432", "ZBE", "postgres", "postgres")
    uri.setDataSource("public","Sample", "geom",csql,"dn")
    vlayer = QgsVectorLayer(uri.uri(), "test", "postgres")
    if not vlayer.isValid():
        print "not valid"
    QgsMapLayerRegistry.instance().addMapLayer(vlayer)
    canvas.refresh()

csql='SELECT field1,field2,etc
  FROM "Trainingset" t, "Polygon" p
  WHERE ST_Intersects(t.geom, p.geom)'

CREATE VIEW boo AS SELECT * FROM p1, p2 WHERE ST_Intersects(p1.geom, p2.geom)

csql = "p1.id IN (SELECT p1.id FROM p1, p2 WHERE ST_Intersects(p1.geom, p2.geom)"