Hi Denis, I proposed this a couple of years ago: http://osdir.com/ml/qgis-user-gis/2011-07/msg00313.html
But no-one dared to implement it until now. Meanwhile the expressions are almost like "virtual columns" - but for some purposes it would still be good to have (e.g. in forms, for QGIS server outputting calculations, etc.). I can also see virtual columns that are aggregates of linked tables (e.g. the sum/min/max of linked records). So I would also like to support such a development if someone wants to do the work. Andreas Am 03.03.2014 14:49, schrieb Denis Rouzaud: > Hi all, > > I was wondering about the idea of being able to create simple views in > QGIS, "views" in terms of database. > Often, I use views (in postgres) to be able to create labels, title, > simple calculation or whatever and also to combine data from joined tables. > > Somehow, all is already there in QGIS but in distinct features: > - joins which will add the fields of the joined table to the main table > - expressions are used in many places where views are meaningful: > labels, styling, search, etc. > - field calculation > > I was thinking that these features should be grouped and improved in > what could be called virtual fields -- so basically a "live" field > calculation without writing to the provider. > > First, the idea would be to define virtual fields using expressions. > > Then, it should be made possible to integrate the joined fields in qgis > expressions without adding them to the current attributes (as it is now). > One way to to it could be a function: joinField( joinName, joinedFieldName) > Hence, the user would be allowed to choose which joined fields he really > wants to be accessible in the layer. > > I believe this is a deep refactoring of the fields behavior, isn't it? > This could be a chance to clean up the joins, which I believe are a bit > messy now. > > This is totally above my skills and somehow my available time, but I > would have (a part of) funding for this. > > What do you think of this idea? > Would it be "easily"achievable without breaking the API? > Would you be interested in taking part of the dev? > > Cheers, > > Denis > > > > _______________________________________________ > Qgis-developer mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-developer _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
