DBMS · Question 27 · Hard
Relation R(A, B, C, D) has the functional dependencies A → B, B → C and C → A. How many candidate keys does R have?
- 3
- 1
- 2
- 4
Answer and explanation
Answer: A. 3
Explanation: D appears on no right-hand side, so every key contains D. A, B and C each determine the other two, so AD, BD and CD each determine all four attributes, and none has a smaller key inside it. That gives 3 candidate keys.
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