What are the first three normal forms and why do they matter?

1NF: Every column holds atomic (indivisible) values. No arrays, no comma-separated lists. Each row is unique. Example violation: storing 'Engineering, Marketing' in a single column. 2NF: 1NF + no partial dependencies. Every non-key column must depend on the ENTIRE primary key (relevant when PK is composite). Example violation: storing product_name in order_items when PK is (order_id, product_id) —