JOIN
command
Combines rows from two or more tables. INNER returns matching rows; LEFT returns all left rows.
Syntax
SELECT ... FROM t1 INNER JOIN t2 ON t1.id = t2.t1_id;
Example
sql
-- INNER JOIN (only matching rows)
SELECT orders.id, users.name, orders.total
FROM orders
INNER JOIN users ON orders.user_id = users.id;
-- LEFT JOIN (all orders, even without user)
SELECT posts.title, users.name AS author
FROM posts
LEFT JOIN users ON posts.user_id = users.id;
-- Multiple joins
SELECT o.id, u.name, p.title
FROM orders o
JOIN users u ON o.user_id = u.id
JOIN products p ON o.product_id = p.id;