Relation \(R\) has eight attributes \(ABCDEFGH\). Fields of \(R\) contain only…

2013

 Relation \(R\) has eight attributes \(ABCDEFGH\). Fields of \(R\) contain only atomic values.

\(F={CH→G, A→BC, B→CFH, E→A, F→EG}\) is a set of functional dependencies (FDs) so that \(F^+\) is exactly the set of FDs that hold for \(R\).

The relation R is

Answer: A. in 1NF, but not in 2NF.Answer: R is in 1NF but not in 2NF. 1NF: Satisfied because every field contains only atomic values. Find candidate keys: D does not appear on the right side…

  1. A.

    in 1NF, but not in 2NF.

  2. B.

    in 2NF, but not in 3NF.

  3. C.

    in 3NF, but not in BCNF.

  4. D.

    in BCNF.

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Correct answer: A

Answer: R is in 1NF but not in 2NF.

  • 1NF: Satisfied because every field contains only atomic values.

  • Find candidate keys: D does not appear on the right side of any functional dependency, so every candidate key must include D.

    1. Closure of B,D: Start with {B,D}. B → C,F,H adds C,F,H. F → E,G adds E,G. E → A adds A. A → B,C adds B,C. Closure yields all attributes A,B,C,D,E,F,G,H, so {B,D} is a candidate key.

    2. Closure of A,D: A → B,C adds B,C. B → C,F,H adds F,H. F → E,G adds E,G. All attributes are obtained, so {A,D} is a candidate key.

    3. Similarly, {E,D} and {F,D} are candidate keys because E → A and F → E,G let them derive all attributes when combined with D.

  • Prime and non-prime attributes: Attributes that appear in some candidate key are prime: A, B, E, F, D. Non-prime attributes are C, G, H.

  • Check 2NF: There is a functional dependency A → B,C. Attribute C is non-prime and is functionally dependent on A, which is a proper subset of the candidate key {A,D}. This is a partial dependency, so the relation violates 2NF.

  • Conclusion: Since 1NF holds but 2NF is violated, the relation is in 1NF but not in 2NF. Consequently it is not in 3NF or BCNF.

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