Database Normalisation

Normalisation is the process of removing redundancy within a database.

Doing so:

Makes accessing and storing data easier and more efficient
Makes maintaining the database contents quicker and easier
Reduces the chances of data errors or duplication.

In order to a achieve this a set of rules were established to achieve efficiency – 1st, 2nd and 3rd normal form. Each rule builds on the last rule, but think of it as a mental process that you go through to improve your database.

Tutorial Video

1st, 2nd and 3rd Normal Form (Database Normalisation) (https://www.youtube.com/watch?v=J-drts33N8g)

Can’t access YouTube? Click Here for the Google Drive version.

First Normal Form “Unique and atomic values”

Each Row in a database must be unique
- Easily achieved through the use of a Primary Key
All cells must only contain one piece of data (no arrays stored in a cell)
All column data must be of the same type

Second Normal Form “No Partial Dependencies”

This is only applicable if the table contains a composite key.
The database must be in First Normal Form
All columns within a table must depend on the whole key (No partial Dependency).

Third Normal Form “No Transitive Dependencies”

The database must be in Second Normal Form
All fields must only be determinable directly by the primary key (no transitive dependency)

Book	Genre	Author	Author Nationality
Twenty Thousand Leagues Under the Sea	Science Fiction	Jules Verne	French
Journey to the Center of the Earth	Science Fiction	Jules Verne	French
Leaves of Grass	Poetry	Walt Whitman	American
Anna Karenina	Literary Fiction	Leo Tolstoy	Russian
A Confession	Religious Autobiography	Leo Tolstoy	Russian