BCFN Normal Form

  • When a prime or a non prime attributes start determining the prime attributes of a table then that table is not in BCNF Normal Form

Example

  • R(A, B, C)
  • Functional Dependency
    • AB–>C
    • C–>B
  • Determining candidate keys by checking closure
    • (A)+ = A –> Not a candidate key
    • (AB)+ = ABC –> Candidate key
    • (AC)+ = ABC –> Candidate key
  • Determining Prime and non prime attribute
    • Prime : ABC
    • Non Prime : None
  • If the relation is in 2NF
    • AB determines C but AB is not a part of candidate key but the entire candidate key
    • C determines B but B is not a non prime attribute.
    • So the relation R is in 2NF
  • If the relation is in 3NF
    • by definition when a non prime attributes starts determining other non prime attributes we call it Transitive dependency which is not allowed in 3NF
    • In our case C determines B but both B and C are prime attributes
    • So the relation R is in 3NF
  • If the relation is in BCNF
    • When a prime or a non prime attributes start determining the prime attributes of a table then that table is not in BCNF Normal Form
    • And yes C is a prime attribute that is determining B which is also a prime attribute then relation R is not in BCNF

Reference :

Example 1

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