GATE | GATE IT 2006 | Question 14

Consider the relations r₁(P, Q, R) and r₂(R, S, T) with primary keys P and R respectively. The relation r₁ contains 2000 tuples and r₂ contains 2500 tuples. The maximum size of the join r₁⋈ r₂ is :

(A) 2000
(B) 2500
(C) 4500
(D) 5000

Answer: (A)
Explanation:

r₁⋈ r₂  is a join operation done on the common attribute R. Further R is the primary key of R2

When we take a , the value of common attribute( R2 in this case) should match.The value of  R in r2 is matched with corresponding R in r1 . So it will have 2000 tuples. So correct option is (A).

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