[postgis-users] Merging two overlapping polygons

[Emilie Laffray]

2009/9/30 Alexandre Dube <adube at mapgears.com>

> Hi,
>
>  I'm looking for a way to merge two overlapping polygons with a sql
> statement.  I've been searching/trying things for a while and still no
> results.
>
>  So far, I'm able to merge all polygons in one using :
>
> SELECT GeomUnion(geom) FROM (SELECT (dump(the_geom)).geom FROM mytable) AS
> s;
>
>  but if I have a third polygon not overlapping the other two, it returns a
> single multipolygon with all three together.
>
>  Any hint ?
>

Performing an intersect check would work I guess if you revamped your query
accordingly.

Emilie Laffray
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