Databases · Relational Model and SQL
Official IIT answer key · IISc Bangalore · Audited Aug 2026
GATE CSE 2024 Set 2 Q45 · MCQ · 2 marks
Person(pid,city), describes the city of residence for every person uniquely identified by pid. The following relational algebra operators are available: selection, projection, cross product, and rename.
To find the list of cities where at least 3 persons reside, using the above operators, the minimum number of cross product operations that must be used isKey concept
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Topic notes
GATE tests the relational model across three interrelated formalisms: Relational Algebra (RA), Relational Calculus (TRC/DRC), and SQL. Questions evaluate core semantic equivalences, translation between declarative calculi and algebraic operators, table instance tracing (such as joins, group-by aggregations, and division), and corner cases like SQL three-valued logic, duplicate preservation, and safe TRC expressions.
Full Relational Model and SQL guide →The relation schema, Person(pid,city) , describes the city of residence for every person uniquely identified by pid . The following relational algebra operators are available: selection , projection , cross product , and rename . To find the list of cities where at least 3 persons reside, using the above operators, the minimum number of cross product operations that must be used is
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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.