Please I should want to receive a suggestion about the creation of db table.
It's a general question not bound strictly with mysql or a particular db.
Think about two practice situations where in the first we can imagine some fields while in the second one there are exactly the same previous fields with another one field in addition.
This last field has no sense for the first situation but has significance only for the second one.
So the question is: in these cases it should be better to create two separate tables or one unique table for both situations leaving this 'different' field empty?
I hope I have explained well the issue.