GATE DA 2026 Set 1 — Question 17
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Database Management & Warehousing → Normalization → Candidate & Super Keys
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Question
be a relational schema with functional dependency set .Which of the following statements is correct?
Correct answer
(A) AD, ED and CD are the only candidate keys of R.
Solution
To find the candidate keys, we determine the closure of attribute sets. Note that does not appear on the right-hand side of any functional dependency, so must be part of every candidate key.Let's test combinations with :
1.Closure of : . Since contains all attributes, is a candidate key.
2.Closure of : . Since contains all attributes, is a candidate key.
3.Closure of : . Since contains all attributes, is a candidate key.
Since is essential, no subset of these keys (like , , or ) can be a key. Also, is not a key because only appears on the RHS and cannot determine other attributes ().Thus, the candidate keys are , , and .Continue learning with Success Tracker
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