What is First normal form (1NF) ?

The term first normal form (1NF) describes the tabular format in which:

All the key attributes are defined.

There are no repeating groups in the table.

All attributes are dependent on the primary key.

What is Second Normal Form (2 NF) ?

It is in 1NF and

It includes no partial dependencies; that is, no attribute is dependent on only a portion of the primary key.

It is still possible for a table in 2NF to exhibit transitive dependency; that is, one or more attributes may be functionally dependent on nonkey attributes.

What is Third Normal Form (3 NF) ?

Create a separate table with attributes in a transitive functional dependence relationship.

A table is in 3NF if:

It is in 2NF and

It contains no transitive dependencies.

Explain Boyce-Codd Normal Form (BCNF) ?

A table is in BCNF if every determinant in that table is a candidate key. If a table contains only one candidate key, 3NF and BCNF are equivalent.

A table is in Boyce-Codd normal form (BCNF) if every determinant in the table is a candidate key.

A determinant is any attribute whose value determines other values with a row.

If a table contains only one candidate key, the 3NF and the BCNF are equivalent.

BCNF is a special case of 3NF.

What is Denormalization?

Normalization is only one of many database design goals.

Normalized (decomposed) tables require additional processing, reducing system speed.

Normalization purity is often difficult to sustain in the modern database environment.

The conflict between design efficiency, information requirements, and processing speed are often resolved through compromises that include denormalization.