[postgis-users] null to zero
Bob Pawley
rjpawley at shaw.ca
Tue Mar 19 10:23:03 PDT 2013
Hi
I am attempting to establish the number of geometries intersecting various polygons and relating the number of geometries to the id of each polygon.
The below works for a single known polygon.
select coalesce (sum(st_numgeometries(foo.edge_data.geom)), 0)
from foo1, foo.edge_data
where st_intersects(foo.edge_data.geom, foo1.five)
and foo1.id = 58
(returns 0)
However I would like to select all the polygons and choose only those intersected by zero or one geometry.
But in the following, as soon as I use the” group by” clause, does not return the coalesced null values, it only returns geometries numbering 1 or more.
select coalesce (sum(st_numgeometries(foo.edge_data.geom)), 0), foo1.id
from foo1, foo.edge_data
where st_intersects(foo.edge_data.geom, foo1.five)
and foo1.id = foo1.id
group by foo1.id
Is there any way of reworking this to obtain polygon ids with null valued intersections??
Bob
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