Suppose R1(A, B) and R2(C, D) are two relation schemas. Let r1 and r2 be the co

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Suppose R1(A, B) and R2(C, D) are two relation schemas. Let r1 and r2 be the corresponding relation instances. B is a foreign key that refers to C in R2. If data in r1 and r2 satisfy referential integrity constraints, which of the following is ALWAYS TRUE?

Options:

A . Ï€B(r1) - Ï€C(r2) = Ã˜

B . Ï€C(r2) - Ï€B(r1) = Ã˜

C . Ï€B(r1) = Ï€C(r2)

D . Ï€B(r1) - Ï€C(r2) â‰ Ã˜

Answer: Option A

-NA-

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