Primary Key

A primary key is a column, or a set of columns, whose value uniquely identifies each row in a database table. No two rows can have the same primary key, and it cannot be NULL.

Each table has at most one primary key. It is often an auto-incrementing number or a UUID rather than real-world data that might change. The database automatically indexes the primary key, and other tables refer to it through foreign keys.

CREATE TABLE students (
  id     INT PRIMARY KEY,
  name   VARCHAR(100) NOT NULL,
  email  VARCHAR(255) UNIQUE
);