This MR imports all building numbers with or without basement. This data gives the building numbers for the combination of main usage status, district id and basement presence. Hence, where ever the number of buildings from this data is inserted the construction material is kept at total and vice versa.
I feel the code possibly looks too complex, and I would like to know if it is true. It will get more complex since I will read a few more CSVs into the import_building_numbers function.