First Normal Form
1NF rules: every column holds atomic (indivisible) values, no repeating groups or arrays in a column, each row is uniquely identifiable by a primary key.
MySQL
Beginner
3 min read
First Normal Form (1NF)
Example
-- Violates 1NF: multiple values in one column
-- id | name | phones
-- 1 | Alice | 555-1111, 555-2222
-- 1NF compliant: one value per cell
CREATE TABLE user_phones (
user_id INT,
phone VARCHAR(20),
PRIMARY KEY (user_id, phone)
); Pro Tip
A column with comma-separated values is a classic 1NF violation.