6. Consider the following two tables TableA aid atext 1 ab 3 TableB bid aid 111 1 123 2 a) (10 points) Assume that aid is the primary key of Table A. Could aid in TableB be used as foreign key, referencing aid in Table A? If not, what changes would be necessary to allow introducing this constraint? b) (5 points) Could bid be made the primary key of TableB? What constraints would have to hold? Do they hold? c) (10 points) If there were a record with bid 222 and aid null in TableB, would this affect questions a) or b)? d) (10 points) What is the result of an inner join of TableA and TableB? e) (10 points) What type of join would represent all records from both tables? Show the result of that type of join.