反转ST_Within查询

Question

I'm using ST_Within, which works fine, but I want to select all points which are not within the convex hull, how do I invert the selection in sql?

SELECT geom FROM pc_processing.pc_201406151141_top top

WHERE st_within(top.geom, (
SELECT st_convexhull(st_collect(geom)) as geom
FROM pc_processing.pc_201407060711_base))

Answer 1

ST_Within returns a boolean, so you can check that the result is false

SELECT geom FROM pc_processing.pc_201406151141_top top
WHERE st_within(top.geom, 
           (SELECT st_convexhull(st_collect(geom)) as geom
            FROM pc_processing.pc_201407060711_base
            )
      ) = false;