Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

-- INNER JOIN — only users who have placed at least one order
SELECT u.name, u.email, COUNT(o.id) AS order_count
FROM users u
INNER JOIN orders o ON o.user_id = u.id
GROUP BY u.id, u.name, u.email;

-- LEFT JOIN — all users, including those with no orders
SELECT u.name, COALESCE(COUNT(o.id), 0) AS order_count
FROM users u
LEFT JOIN orders o ON o.user_id = u.id
GROUP BY u.id, u.name;

-- Find users who have NEVER placed an order
SELECT u.name, u.email
FROM users u
LEFT JOIN orders o ON o.user_id = u.id
WHERE o.id IS NULL;

-- FULL JOIN — all products and all categories, including orphans
SELECT p.name AS product, c.name AS category
FROM products p
FULL JOIN categories c ON c.id = p.category_id;

-- Multiple JOINs — order with customer and product details
SELECT o.id, u.name AS customer, p.name AS product, oi.qty, oi.unit_price
FROM orders o
JOIN users       u  ON u.id  = o.user_id
JOIN order_items oi ON oi.order_id = o.id
JOIN products    p  ON p.id  = oi.product_id
WHERE o.status = 'shipped';