normal forms

Question 1

First normal form

Answer 1

A relation is in first normal form if every attribute in that relation is a single-valued attribute. If a relation contains composite or multi-valued attribute, it violates the first normal form.

Question 2

Second Normal Form

Answer 2

A relation is in second normal form if it satisfies the conditions for first normal form and does not contain any partial dependency. A relation in 2NF has no partial dependency, i.e., it has no non-prime attribute that depends on any proper subset of any candidate key of the table. Often, specifying a single column Primary Key is the solution to the problem.

Question 3

Third Normal Form

Answer 3

A relation is said to be in the third normal form, if it satisfies the conditions for second normal form and there is no transitive dependency between the non-prime attributes, i.e.,all non-prime attributes are determined only by the candidate keys of the relation and not by any other non-prime attribute.

Question 4

Boyce-Codd Normal Form

Answer 4

A relation is in Boyce-Codd Normal Form if satisfies the conditions for third normal form and for every functional dependency, Left-Hand-Side is super key. In other words, a relation in BCNF has non-trivial functional dependencies in the form X –> Y, such that X is always a super key.