Question

If every non-key attribute is functionally dependent on the primary key, then the relation is in _______.
1. First normal form
2. Second normal form
3. Third normal form
4. Fourth normal form

Answer 1

Correct Answer - Option 2 : Second normal form

The correct answer is option 2:

CONCEPT

1NF:

• There are only Single Valued Attributes.
• There is a unique name for every Attribute/Column.

2NF:

• A relation that is in First Normal Form 
• Every non-primary-key attribute is fully functionally dependent on the primary key

 

3NF:

• The third normal form is based on the concept of transitive dependency. A functional dependency X->Y in a relation schema R is a transitive dependency if there exists a set of attributed Z in R that is neither a candidate key nor a subset of any key of R.
• A relation is in 3NF if it satisfies 2NF and no prime attribute of R is transitively dependent on the primary key.
• If X - > A is a functional dependency, then A should be a prime attribute or X should be a candidate key.
• Lossless join and dependency preservation is always possible in 3NF. 3NF decomposition is always lossless join and dependency preserving.

BCNF:

• It stands for Boyce Codd normal form.
• A relation R is in BCNF if whenever a non-trivial functional dependency X -> A holds in R, then X is a superkey of R. Any relation with two attributes is always in BCNF. Because when a relation contains only two attributes then one attribute determines another and the left side of the functional dependency will always be a candidate key in that case.
• BCNF is not always dependency preserving.