Normalisation
Computer Science: OCR A Level, topic 3.2.6
Normalisation to 3NF
Normalising data is a process which makes a database more efficient to run and store.
Stages of normalisation
- To ensure the most efficient database structure possible, we use a process called normalisation.
- There are 3 stages of normalisation:
- First normal form (1NF).
- Second normal form (2NF).
- Third normal form (3NF).
- Normalisation can turn a flat-file database into a relational database.
Unnormalised data
- Before going to 1NF, a flat-file table structure is put together.
- We refer to this stage as unnormalised data or 0NF.
First normal form
- For a database to be in 1NF it has to obey the following:
- No columns with repeated or similar data.
- Each row is unique with a primary key.
- Each field must have a unique name.
Second normal form
- For a database to be in 2NF, it has to be in 1NF.
- Each of the fields must rely on the primary key to be unique.
Third normal form
- For a database to be in 3NF, it has to be in 2NF.
- No field should rely on another non-key field.
- For example, a database should not store someone's age and date of birth.
- It should store the date of birth only and the surrounding software should be used to calculate the age.