merge two csv files into output.csv using Subprocess

[Pedroski55]

@DeaD_EyE after importing from __future__ import annotations it worked perfectly! Now all I need to do is try to understand what's happening!!

@mg24: if the database table is so big, why not export smaller parts? Dump 10 000 rows instead of all rows. Or make a bit of Python to get 10 000 rows at a time from each table and write to csv? That way, you would have nice manageable chunks!