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+15 votes

Let $R = (A, B, C, D, E, F)$ be a relation scheme with the following dependencies $C \rightarrow F, E \rightarrow A, EC \rightarrow D, A \rightarrow B $. Which one of the following is a key for $R$?

  1. CD
  2. EC
  3. AE
  4. AC
asked in Databases by Veteran (52k points) | 706 views

1 Answer

+20 votes
Best answer
Answer: B

EC is the key for R. Both E and C are not coming on the right hand side of any functional dependency. So, both of them must be present in any key. Now, with EC and the given FDs, we can derive all other attributes making EC a key.
answered by Boss (33.8k points)
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