I have a line (pipe) network. Based on 3 attributes (material, dimension, location-street) I created new attribute with the same material, dimension and location. Now I want to dissolve the network based on this new attribute. Problem is, often location is "Null" (pipe is not in the street). Simple dissolving therefore create many multiparts with same material and dimension. These multiparts are often not part of the same line, e.g. multiparts with 2 parallel segments or simply far from each other. How can I solve this problem?