For the relations s and r in your study manual of our chapter 2 (i.e., joining two relations),
suppose we type a collection of relational algebra queries, and get the following results.
A B C D E
A 2 a 10 B
b 2 a 10 b
Please explain how this happened? If you think this result could happen in practice, please write the
corresponding relational algebra queries; otherwise, please explain why.