The SQL implementation for finding users with failed orders

why_learn_sql.sql

/* Naive Python implementation */
SELECT *
FROM orders
WHERE NOT payment_status

-- Loop over the results from previous query
-- and run this select each time
SELECT *
FROM users
WHERE id = '{{ user_id }}'


/* SQL implementation */
SELECT DISTINCT users.*
FROM users
INNER JOIN orders
  ON users.id = orders.user_id
WHERE NOT orders.payment_status