Part 141: Database Normalization: 1NF, 2NF & 3NF Explained

Normalization organizes database schemas to reduce data redundancy and eliminate insert, update, and delete anomalies.

1. The Normal Forms

1NF (First Normal Form)

• Each column must contain atomic (indivisible) values.
• No repeating groups or arrays stored in a single text field (e.g. 'tag1,tag2,tag3').

2NF (Second Normal Form)

• Must be in 1NF.
• All non-key attributes must depend on the entire primary key (no partial dependencies on composite keys).

3NF (Third Normal Form)

• Must be in 2NF.
• No transitive dependencies: Non-key attributes must depend directly on the primary key, and not on other non-key attributes (e.g. store department_id, not department_name and department_manager inside the employee table).

Key Takeaways

• 3NF ensures every attribute depends on "the key, the whole key, and nothing but the key, so help me Codd".

In Part 142, we explore BCNF & Higher Normal Forms!