+1 dedicated primary key field each time an object is edited (split/delete/merge) the fid is thrown away and renewed. This is at the base level. It has to be that way to keep the relationship between the diffent files "in" the shapefile related. (i.e. dbf, shx, shp). As haubourg suggests - create a new field and calculate the fid into it. However there is another fallacy with what you propose. The FID between two shape files cannot be relate-able (the same record to record) unless they are exact duplicates of each other. (There seems to be no logical reason for creating that type of join). In order to accomplish joining two spatially relate-able feature classes (point/polygon). You should first decide what you want to know. 1. how many points are in each polygon? 2. which points are in which polygon? http://qgis.spatialthoughts.com/2012/02/tutorial-spatial- analysis-points-in.html 1. you can also do a spatial join using table manager (after the create field step above in the point file). and then relate the newly created table back to the . The opposite one will depend on the direction of your spatial join and what you are trying to accomplish. http://gis.stackexchange.com/questions/29756/how-to- install-ftools-and-table-manager qgis join http://docs.qgis.org/html/en/docs/user_manual/working_with_ vector/vector_properties.html#index-28
On Mon, Dec 3, 2012 at 4:51 AM, haubourg < [email protected]> wrote: > Hi, > FID must be considered as internal identifiers , that can be unstable. I > guess this is the reason why it is not exposed by gdal drivers and others. > You should create a dedicated primary key field, this is a better pratice, > less risky if data changes. > Régis > > > > -- > View this message in context: > http://osgeo-org.1560.n6.nabble.com/How-to-join-shapefile-tables-via-their-FIDs-tp5020215p5020305.html > Sent from the Quantum GIS - User mailing list archive at Nabble.com. > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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