Hi all Thanks for your positive (and fast!) replies. I'll be giving the RT Sql layer plugin a try and I'll also investigate whether this functionality is available (using python scripting) with spatialite layers.
Jurgen: thanks for the SQL EXISTS tip. I have to brush up on my SQL ;) Still I didn't know that it is possible to use other table names in QGIS's Query Builder. On Thu, Sep 30, 2010 at 1:27 PM, Jürgen E. <j...@norbit.de> wrote: > Hi Carson, > > On Thu, 30. Sep 2010 at 13:18:46 +0100, Carson Farmer wrote: >> http://www.carsonfarmer.com/?p=713 >> and the RT Sql Layer plugin >> > 1 - Is it possible to build a query where two (or more) layers are >> > involved? Something like: >> > >> > SELECT a.* >> > FROM a, b >> > WHERE Contains(b, a) > > and that simple case can be expressed as exists expression in the query > builder > (for postgres and spatialite). Create a layer from a and use following query > string: > > exists (select * from b where contains(b.geom,a.geom)) > > Creating views is another option (but you still need a unique 32bit integer > primary key for the feature ids, which might be hard to generate in some > cases). > > > Jürgen > > -- > Jürgen E. Fischer norBIT GmbH Tel. +49-4931-918175-20 > Dipl.-Inf. (FH) Rheinstraße 13 Fax. +49-4931-918175-50 > Software Engineer D-26506 Norden http://www.norbit.de > > -- > norBIT Gesellschaft fuer Unternehmensberatung und Informationssysteme mbH > Rheinstrasse 13, 26506 Norden > GF: Jelto Buurman, HR: Amtsgericht Emden, HRB 5502 > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user > -- ___________________________ ___ __ Ricardo Garcia Silva _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user