joins_sql_styleguide.sql

-- Bad: multiple type of joins unecessarily used, start from `orders` as base table is not ideal
SELECT
  DATE(orders.created_at) AS date,
  users.email
FROM orders
LEFT JOIN users
       ON users.id = orders.user_id
JOIN order_items
  ON order_items.order_id = orders.id
GROUP BY 1, 2
HAVING COUNT(order_items.id) > 10

-- Good:
SELECT
  DATE(orders.created_at) AS date,
  users.email
FROM order_items
LEFT JOIN orders
       ON orders.id = order_items.order_id
LEFT JOIN users
       ON users.id = orders.user_id
GROUP BY 1, 2
HAVING COUNT(order_items.id) > 10