I've just done a mini test and scored 9/10, however, from my understanding, I think this question is incorrect. Here is the only question which I don't understand how it can be correct:So I joined up the relations and get this: A | R.B | S.B | C | D 1 |  2  |  2  | 4 | 6   //this meets theta-condition R.A<S.C AND R.B<S.D3 |  4  |  4  | 6 | 8   //this meets theta-condition R.A<S.C AND R.B<S.D3 |  4  |  4  | 7 | 9   //this meets theta-condition R.A<S.C AND R.B<S.D5 |  6So the potential answers are:1,2,2,4,63,4,4,6,83,4,4,7,9But, as seen in the question I do not have matching-solution for any of these and I made an educated guess and concluded that there was a mistake in the paper... or did I make the mistake?
Relational Algebra - Mistake in the quiz?
relational algebra