Gate CS-2018 Question Paper With Solutions

Q. 59 Consider the relations r(A, B) and s(B, C), where s.B is a primary key and r.B is a foreign key referencing s.B. Consider the query

Q: r⋈(σ_B<5(s))Let LOJ denote the natural left outer-join operation. Assume that r and s contain no null values.

Which one of the following is NOT equivalent to Q?

(A) σ_B<5(r ⋈ s)

(B) σ_B<5(r LOJ s)

(C) r LOJ (σ_B<5(s))

(D) σ_B<5(r)LOJ s

Answer: (C)

Explanation: