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Reputation: 298

Are these two definitions of relational division equivalent?

I saw two kinds of relational division definition expressions.

relational division:

R(E,I)÷S(I)={r.E | r∈R and ∀(s∈S)∃(t∈R)(t.E=r.E and t.I=s.I)}

From the book "Database Management Systems" (third edition, page 109, chapter 4.2.5) by Raghu Ramakrishnan and Johannes Gehrke:

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Are those two expressions defining relational division equivalent?

How do I prove strictly that they are equivalent?

Upvotes: -1

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