Let R and S be relational schemes such that R={a,b,c} and S={c}. Now consider the following queries on the database:

IV) SELECT R.a, R.b
       FROM R,S
            WHERE R.c=S.c

Which of the above queries are equivalent?
(A) I and II
(B) I and III
(C) II and IV
(D) III and IV


Answer: (A)

Explanation: I and II describe the division operator in Relational Algebra and Tuple Relational Calculus respectively. See Page 3 of this and slide numbers 9,10 of this for more details.

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