If your query is very common, you might want to consider making a database VIEW, so you can add the dynamic layer whenever you want. To do this, just tailor your SELECT statement so it shows the right columns, including geometry and a unique integer column (this can be tricky).
For PostGIS, I'd suggest adding the VIEW using PgAdmin. You can optionally add the geometry_column metadata manually (although QGIS picks this out automagically). For SpatiaLite, see: http://www.gaia-gis.it/spatialite-2.4.0/Using-Views-Basic.pdf -Mike On 30 September 2010 05:47, Ricardo Filipe Soares Garcia da <[email protected]> wrote: > 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. <[email protected]> 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 >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> > > > > -- > ___________________________ ___ __ > Ricardo Garcia Silva > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
