Take the 2-minute tour ×  Here's a quick summary about what I'm
trying to do: Let's say I got two layers. One (A) with 10
polygons and one that is more granular with 100 polygons (B).
Just to check if the behavior of PostGIS and ArcMap is the same,
I would like to select all polygons in B that are under a
polygon in A. Since the sum of all polygons of both layer got
the same shape, all polygons of B should be selected. If I do
that in ArcMap, everything works fine (100 of 100 polygons
selected). If I use the following statement in PostGIS, some of
the polygons are not in the resultset (about 10%):  SELECT
layer_a.gid, layer_b.gid FROM layer_a, layer_b WHERE
ST_Contains(layer_a.geom, layer_b.geom);  No I want to be more
specific. Let's say I'd like to select all Polygons from B that
are under a specific polygon from A with a polygon_id = 1. For
this I use the following statement:  SELECT layer_a.gid,
layer_b.gid FROM layer_a, layer_b WHERE
ST_Contains(layer_a.geom, (SELECT layer_b.geom WHERE
layer_by.polygon_i