Database Normalization Guide

What is Normalization?

Normalization organizes database tables to reduce redundancy and improve data integrity. It splits data into related tables following normal forms.

The Problem It Solves

-- ❌ Unnormalized — repeated data
Orders: id | customer | customer_email | product
        1  | Sara     | sara@x.com     | Pen
        2  | Sara     | sara@x.com     | Book   ← email repeated

The Normal Forms

Form	Rule
1NF	Atomic values, no repeating groups
2NF	1NF + no partial dependencies
3NF	2NF + no transitive dependencies

Normalized Version

Customers: id | name | email
Orders:    id | customer_id | product
-- Email stored once, referenced by ID

Trade-offs

Normalization reduces redundancy but adds JOINs. Sometimes you denormalize for read performance.

FAQs

How far should I normalize?

3NF is enough for most apps. More in our Database guides.

What is denormalization?

Deliberately adding redundancy to speed up reads.