The ON clause

Choose which column to match on.

Table aliases

In JOINs you alias table names for brevity. With FROM orders o you give the alias o.

SELECT o.id, c.name
FROM orders o
JOIN customers c ON o.customer_id = c.id;

This query orders aliased as o, customers as c.

o.id, c.name is selected from orders o. customers c is joined on o.customer_id = c.id, keeping only matching rows.

Aliases shorten long table names and make queries readable. ON and SELECT use the alias; the AS keyword is optional.

INNER JOIN orders o and customers c; select o.id and c.name.

Show example solution

SELECT o.id, c.name
FROM orders o
JOIN customers c ON o.customer_id = c.id

Alias

SELECT o.id FROM orders ____ JOIN customers c ON o.customer_id = c.id;

Show answer

SELECT o.id FROM orders o JOIN customers c ON o.customer_id = c.id;