V 8.4 of postgres supports recursive (heirarchical) queries, which may be able
to do something useful in this area.
Cheers,
Brent Wood
--- On Thu, 7/8/10, Birgit Laggner wrote:
From: Birgit Laggner
Subject: Re: [postgis-users] ESRI union (analysis) in Postgis
To: postgis-users
Hi Teresa,
I'm struggeling with the translation of the union (analysis) tool of
ArcGIS into PostGIS myself since a while. The problem is, that in
PostGIS, you always compare one row of the first data set with one row
of the second data set. That means, that interaction of more than 2
polygons is a
Hi Teresa,
you can't get a intersection from more then two polygons at a time. Think
about the attributes you get. The attributes are from poly1 and or poly2. The
solution is to use only datasources with non overlaping polygons.
Gr
Ralf
Am Donnerstag 08 Juli 2010, 09:27:06 schrieb Teresa Fazio
The solution you propose is valid to get polygons describing
intersections between two polygons, but I cannot figure out how to
obtain polygons describing intersections between more than two polygons
like the central polygon drawn in the shape TEST_Union.
I repeat that the TEST_Union shapefile w
Hi Teresa,
you can enhance the following construct to fit your needs.
CREATE VIEW fakeunion AS
-- poly1 only
SELECT a, b, NULL AS c, NULL AS d, geom
FROM poly1
WHERE gid NOT IN
(
SELECT p1.gid
FROM poly1 p1
INNER JOIN
poly2 p2 ON (ST_Intersects(p1.geom,p2.g
