Normalisation (1NF, 2NF, 3NF)

Normalisation is the process of organising a database to reduce redundancy (unnecessary duplication of data) and improve data integrity. It involves applying a series of rules called normal forms to decompose tables into a better structure.

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Why Normalise?

Without normalisation, databases can suffer from:

Problem	Description
Insertion anomaly	Cannot add data without unrelated data already existing (e.g. cannot add a new course without a student enrolled on it)
Deletion anomaly	Deleting one piece of data accidentally removes other valuable data
Update anomaly	Changing data in one place but not everywhere it appears, leading to inconsistency
Data redundancy	The same data is stored multiple times, wasting space and risking inconsistency

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Unnormalised Form (UNF)

Data in its raw, unprocessed state — often containing repeating groups, multi-valued fields, or nested data.

Example — Unnormalised Student-Course Data:

StudentID	Name	Courses
101	Alice	Maths, Physics, CS
102	Bob	English, CS
103	Carol	Maths, English, History, CS