3RD AND BC NORMAL FORM IN DBMS (3rd NF and BCNF)

                                                         

                         

THIRD NORMAL FORM

A relation is said to be in third normal form when all transitive dependencies are removed from the table or database that is no transitive dependency for the nonprime attributes. 3rd normal form is implementing after the 1^st and 2^nd NF. A general Example:-

A, B, C are three columns in table

1.          If C is belonging to B
2.          If B is belonging to A
3.          Then C is indirectly belonging to the A

In above example, there are contains transitive dependency.

 

This problem can be solved using a foreign key that column id(students), id(Subject) must be placed in the third table.

 

BOYCE-CODD NORMAL FORM

This form was developed by R.F. Boyce and E.F. Codd in 1974. It is an advanced version of the 3^rd NF (third normal form). It was found to be stricter than 3NF because every relation in BCNF is also in 3NF. A relation schema R is in BCNF if whenever a nontrivial functional dependency X -> A holds in R, then X is a super key of R.

College of Engineering Roorkee 

Difference between 3NF and BCNF:-

 BCNF

• It is stronger compare to the 3^rd NF.
• Functional dependencies on 1^st NF, 2^nd NF, and 3^rd NF.
• Any relation A -> B, A should be the super key of the relation.
• The redundancy is loose compare to 3^rd NF
• BCNF is difficult to achieve.

3^rd NF

•          It is not stronger compare to the BCNF.
•          It is function dependency on 1^st NF and 2^nd NF.
•          No transitive dependency
•          It is easy to achieve.