Use dmax parameter to control query distance tolerance (how far points/centroids can be from qvector features). For more options, use v.distance instead. In case of a multipoint input vector map, with several points having the same category number, it can happen, that the query result is NULL, if the same category number falls into different qvector polygons. When transferring attributes from a point map to a polygon map, usually dmax has to be larger than zero (determined by distance between query points and polygon centroids). In this example, city names, population data and more from Geonames.org country files are transferred to selected EU CORINE landuse/landcover classes ('Continuous urban fabric', 111, and 'Discontinuous urban fabric', 112). Note: Example in UTM projection to which the input maps have been projected beforehand to have metric distances support: Source.