Let R and S be two relations with the following schema
R (P, Q, R1, R2, R3)
S (P, Q, S1, S2)
Where {P, Q} is the key for both schemas. Which of the following queries are equivalent?
I) ΠP (R ⋈ S)
II) ΠP (R) ⋈ ΠP (S)
III) ΠP (ΠP, Q (R) ∩ ΠP, Q (S))
IV) ΠP (ΠP, Q (R) - (ΠP, Q (R) - ΠP, Q (S)))
1
Only I) and II)
2
Only I) and III)
3
Only I), II) and III)
4
Only I), III) and IV)
5
Question Not Attempted