Normalization

Database normalization is a technique, which is dealing with relational database management systems.

Normalization is used to reduce the data redundancy of the database. That means implementing database tables and their relationships, eliminating redundancy and inconsistent dependency. There are some predefined rules set for normalization. Those rules are called normal forms.

First Normal Form (1NF)
First Normal Form is referred to as the atomicity of a table. Table atomicity can be reached from two steps.

• Removing duplicate columns from the same table.
• Creating separate tables for related duplicated columns. ( there must be primary keys to identify each row of this tables)

Second Normal Form(2NF)
2NF should meet all the needs of 1NF and there must not be any partial dependency of any column on primary key.

Third Normal Form(3NF)
3NF applies that every non-primary attribute of table must be dependent on primary key. The transitive functional dependency should be removed from the table. The table must be in second Normal Form.

The advantage of removing transitive dependency is,

• amount of data duplication is reduced.
• data integrity achieved.

BCNF
BCNF is a higher version of the 3NF. this form deals with certain type of anomaly that is not handled by 3NF.A 3NF table which does not have multiple overlapping candidate keys is said to be in BCNF.

Fourth Normal Form(4NF)
4NF meets all the requirements of the 3NF and a relation is in 4NF if it has no multi-valued dependencies

What is the difference between BCNF and 4NF (Fourth Normal Form)?

•Database must be already achieved to 3NF to take it to BCNF, but database must be in 3NF and BCNF, to reach 4NF.

• In fourth normal form, there are no multi-valued dependencies of the tables, but in BCNF, there can be multi-valued dependency data in the tables.