UGC-NET | UGC-NET CS 2017 Nov – III | Question 9

If every non-key attribute is functionally dependent on the primary key, then the relation is in __________ .
(A) First normal form
(B) Second normal form
(C) Third normal form
(D) Fourth normal form


Answer: (B)

Explanation: Conditions for various normal forms:

  1. 1 NF – A relation R is in first normal form (1NF) if and only if all underlying domains contain atomic values only.
  2. 2 NF – A relation R is in second normal form (2NF) if and only if it is in 1NF and every non-key attribute is fully dependent on the primary key.
  3. 3 NF – A relation R is in third normal form (3NF) if and only if it is in 2NF and every non-key attribute is non-transitively dependent on the primary key.
  4. BCNF – A relation R is in Boyce-Codd normal form (BCNF) if and only if every determinant is a candidate key.

Example:
Relation R(XYZ) with functional dependencies {X -> Y, Y -> Z, X -> Z}.
This relation is in 2NF but not in 3NF because of every non-key attribute is transitively dependent on the primary key. Here {X} will be candidate key.

So, option (B) is correct.

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