Keys and Constraints in MySQL

Published on: July 26, 2025 | Published by: Sai Sreeram Gundepudi

Primary Key

CREATE TABLE customers (
  id INT PRIMARY KEY,
  name VARCHAR(100)
);

Foreign Key

CREATE TABLE orders (
  id INT PRIMARY KEY,
  customer_id INT,
  FOREIGN KEY (customer_id) REFERENCES customers(id)
);

Other Constraints

NOT NULL
UNIQUE
DEFAULT