[postgis-users] polygons inside polygon

Nicolas Ribot nicolas.ribot at gmail.com
Tue Nov 30 10:16:47 PST 2021


What about a simple left join on the table searching for polygons contained
inside other polygon ?
Polygons that are contained inside other polygons will have false for the
outer_pg column and true if they are not contained (ie are outer polygons).
You can then create the tables you want based on the outer_pg values

select distinct p1.id, p2.id is null as outer_pg
from polygon p1
     left join polygon p2 on p1.id <> p2.id and st_within(p1.geom, p2.geom)
order by p1.id;

id	outer_pg
1	true
2	true
3	true
4	true
5	false
6	false
7	false
8	true
9	true
10	true
11	false

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