GATE 2011 CS (CS1) – Question 56

Databases · Relational Model: Relational Algebra, Tuple Calculus, SQL · 2 marks · Multiple choice

Loan_Records(Borrower,Bank_Manager,Loan_Amount) contains (Ramesh,Sunderajan,10000),(Suresh,Ramgopal,5000),(Mahesh,Sunderajan,7000). Find the output.

SELECT count(*)
FROM (SELECT Borrower,Bank_Manager FROM Loan_Records) AS S
NATURAL JOIN
     (SELECT Bank_Manager,Loan_Amount FROM Loan_Records) AS T;

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Show answer and explanation

Correct answer: (C) 5

Explanation

The natural join matches the shared Bank_Manager attribute. Sunderajan has two rows on each side, contributing 2×2=4 joined rows. Ramgopal has one on each, contributing one. Total count is five, C; joining the separate projections does not restore only the original borrower/amount pairing.

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