SQL — JOIN

Overview

JOIN combines rows from two tables using a related key.

What you'll learn

• INNER JOIN
• LEFT JOIN
• ON condition
• table aliases

Syntax

SELECT ... FROM a JOIN b ON a.id=b.a_id;

Example

SELECT u.name, o.total
FROM users u
JOIN orders o ON o.user_id = u.id
ORDER BY o.total DESC;

Notes

• Index join keys for speed.
• LEFT JOIN keeps rows from the left table.

  Try: Open the Playground: /en/playground/sql