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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
in Databases 1.8k views

1 Answer

26 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.

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