GATE CS 2026 Set 1 — Question 65
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Databases → Relational Model → Keys (Super, Candidate, Foreign)
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Question
Consider a relational database schema with a relation
(answer in integer)
R(A, B, C, D). If and are the only two candidate keys of the relation , then the number of superkeys of relation is ______.(answer in integer)
Correct answer
6 to 6
Solution
Given a relation
R(A, B, C, D) with attributes and candidate keys and .A superkey is a set of attributes that contains at least one candidate key.1.Let be the set of superkeys containing . The remaining attributes are . The number of superkeys is .
These are: .2.Let be the set of superkeys containing . The remaining attributes are . The number of superkeys is .
These are: .3.To find the total number of unique superkeys, we use the principle of inclusion-exclusion: .
4.The intersection consists of superkeys that contain both and , which means they must contain . The remaining attribute is . The number of such superkeys is .
These are: .Total number of superkeys .Continue learning with Success Tracker
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