DBMS · Question 7 · Medium
Relation R(A, B, C, D, E) has the functional dependencies A → B, B → C and CD → E. Which of the following is a candidate key of R?
- A
- AD
- AB
- CD
Answer and explanation
Answer: B. AD
Explanation: A and D never appear on the right-hand side, so every key must contain both. {A, D}+ = {A, D, B, C, E}, which is all attributes, so AD is a candidate key. A+ = {A, B, C} only.
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