[postgis-users] Anti st_union
simon at spatialdbadvisor.com
Fri Oct 16 15:40:21 PDT 2009
> In order to have only one row, I have a number of points stored in a table as st_union.
I assume you mean stored in a table as a MULTIPOINT geometry?
> Is there a method of breaking the points out of the st_union geometry so that I can access the points individually.
> I want to use the points as a reference for st_within. It doesn't seem to works as it seems to regard the st_union point geometry as a whole.
Here is an example of what I think you want using 10 points dynamically generated, unioned and then Dumped.
select (ST_Dump(MPoint)).geom as Point
from (select ST_Union(ST_Point(g.*,g.*)) as MPoint
from generate_series(1,10,1) g
) as m;
select ST_GeometryN(f.MPoint,f.pcount) as Point
from (select m.MPoint, generate_series(1,ST_NumGeometries(m.mpoint),1) as pcount
from (select ST_Union(ST_Point(p.*,p.*)) as MPoint from generate_series(1,10,1) as p ) m
) as f;
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