I have two applications need to 'merge' them to one and the second uses a lot of tables of the first. The thing is what is the best choice I can have based on the efficiency of data and speed. If it's double keys then I need to create null values because their purpose is different. If it's double tables then all the fields are doubled.
choice1: double keys renamed
choice2: double tables renamed
choice3:n something else... TELL WHAT please