Part 68: Multi-Table Joins: Joining 3 or More Tables

Real-world business queries span multiple normalized tables.

1. Complete E-Commerce Order Details Query

SELECT 
  o.id AS order_id,
  u.first_name || ' ' || u.last_name AS customer_name,
  p.name AS product_name,
  oi.quantity,
  oi.unit_price,
  (oi.quantity * oi.unit_price) AS line_total
FROM orders o
JOIN users u ON o.user_id = u.id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id
WHERE o.status = 'shipped'
ORDER BY o.id, line_total DESC;

Key Takeaways

• Chain joins sequentially following foreign key relationships.

In Part 69, we explore Non-Equi Joins: Joining on Ranges and Inequalities!