[postgis-users] Comparison of geometries

[Düster Horst]

I try to compare two geometry tables with the intension to detect the
geometrical and attributive differences between these two tables. For
example I attach two tables new and old. Now I want to detect all geometries
of the table old which are not in table new. For this issue I use the
following query

select the_geom, art from "old"
except 
select the_geom, art from "new"

but the query doesn't supply the correct result. The correct result should
contain two records but the query results 0 records. Now I'm doubt about
whether  it's allowed to use geometries in an except clause like other
datatypes?? Otherwise in other tables 100% of different geometries will be
detected by the query above!

My System:
RedHat AS4
PostgreSQL 8.1.1
POSTGIS="1.0.6" GEOS="2.1.1" PROJ="Rel. 4.4.8, 3 May 2004" USE_STATS
DBPROC="0.3.0" RELPROC="0.3.0"

I'll appreciate every hint.

Best regards
 
Dr. Horst Düster 
GIS-Koordinator, Stv. Amtsvorsteher

Kanton Solothurn 
Amt für Geoinformation
Abteilung SO!GIS Koordination
Rötistrasse 4
CH-4501 Solothurn 

Tel.: ++41 (0)32 627 25 32 
Fax: ++41 (0)32 627 22 14

horst.duester at bd.so.ch 
www.sogis.so.ch


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