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There is some mistake in question.
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⋈(σB<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) σB<5(r ⋈ s)
(B) σB<5(r LOJ s)
(C) r LOJ (σB<5(s))
(D) σB<5(r)LOJ s
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There is some mistake in question. 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⋈(σB<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) σB<5(r ⋈ s) (B) σB<5(r LOJ s) (C) r LOJ (σB<5(s)) (D) σB<5(r)LOJ s