I need to join the attributes of a shapefile with the one contained in a .dbf (or .txt) file. I currently use the "join" in the properties menu, but I have a problem. In the shapefile I have one identity code for each building; in the .dbf (or .txt) I have several noise levels related to the several façades of the same building. So when I use "Join" I miss some data because the results is only one value that seems to be taken from the last point considered in the merge of the properties. Is it possible to do this operation in a different way? For instance taking the minimum, the maximum and/or the average value of the noise level... Thanks a lot in advance for your useful suggestions!