DATABASE NORMALISATION

DATABASE NORMALISATION

"The Key, the Whole Key and, Nothing but the Key, so help me Codd."

BCNF

3NF

2NF

1NF

UNF

Second Normal Form

Boyce-Codd Normal Form

Third Normal Form

First Normal Form

Un-Normalised Form

Un-Normalised Form

This is a database data model that does not meet any of the conditions of database normalisation, as defined by the relational model. This is because it is either; a NoSQL database, or a database at the start of the normalisation process.

Boyce-Codd Normal Form

Boyce-Codd normal form is also known as 3.5NF, as it is a slightly stricter version of the third normal form.By using BCNF, a database will remove all reduncancies based on functional dependencies.

First Normal Form

A relation is in the first normal form 'if and only if' no attribute domain has relations as elements. I.e. no table column can have tables as values.

Second Normal Form

A relation is in the second normal form if:

• It is in the first normal form.
• It has a unique identifier (UID), can be multi-attribute or single attribute.

Third Normal Form

A relation is in the third normal form if:

• It is in the first & second normal forms.
• For every non-trivial functional dependency X -> Y, X is a superkey or Y\X consists of prime attributes.

Note: This is a simplification/snippet, not the full definition.