Consider a relation R with attributes {A, B, C} and functional dependency set S = {A → B, A → C }. Then relation R can be decomposed into two relations : 

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  1. R1{A, B} AND R2 {A, C} 
  2. R1{ A, B} AND R2{ B, C} 
  3. R1{A, B, C} AND R2{A, C}
  4. None of the above

Answer (Detailed Solution Below)

Option 1 : R1{A, B} AND R2 {A, C} 
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The correct answer is Option 1.

Key Points

  • Given a relation R with attributes {A, B, C} and a functional dependency set S = {A → B, A → C}, we can decompose the relation R into two relations.
  • Option 1 suggests decomposing R into R1{A, B} and R2{A, C}.
  • To verify the correctness of the decomposition:
    • We need to check if both decomposed relations are in BCNF (Boyce-Codd Normal Form) or at least 3NF (Third Normal Form).
    • In R1{A, B}, the functional dependency A → B holds, and A is a candidate key for R1, satisfying BCNF.
    • In R2{A, C}, the functional dependency A → C holds, and A is a candidate key for R2, satisfying BCNF.
  • Thus, the decomposition is lossless and dependency preserving, making Option 1 the correct choice.

Additional Information

  • Decomposition is a process of breaking down a relation into smaller relations to achieve normalization and eliminate redundancy.
  • BCNF is a stricter version of 3NF where every determinant is a candidate key.
  • Ensuring that decomposed relations are in BCNF helps maintain data integrity and avoid anomalies during database operations.
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