DBMS · Question 21 · Medium
Relation R(A, B, C, D, E) has the functional dependencies A → B, BC → D and D → E. What is the attribute closure (AC)+?
- ABCDE
- ABC
- ABCD
- AC
Answer and explanation
Answer: A. ABCDE
Explanation: Start with {A, C}. A → B adds B; BC → D adds D; D → E adds E. So (AC)+ = {A, B, C, D, E}, which also makes AC a key of R.
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