What is First Normal Form (1NF)?

A table is in First Normal Form (1NF) when: 1) All column values are atomic (indivisible — no arrays, lists, or nested structures in a single column). 2) Each column holds values of a single type. 3) Each column has a unique name. 4) The order of rows does not matter. Example violation: a phone_numbers column containing "555-1234, 555-5678" (multiple values). Fix: create a separate phone_numbers table with one number per row. 1NF is the foundation all other normal forms build upon.