Part 81: Introduction to Common Table Expressions (WITH Clause)

A Common Table Expression (CTE) defines a temporary, named result set that exists only within the execution scope of a single SQL statement.

1. Syntax

WITH HighValueOrders AS (
  SELECT customer_id, SUM(total_amount) AS customer_total
  FROM orders
  GROUP BY customer_id
  HAVING SUM(total_amount) > 5000.00
)
SELECT c.name, c.email, hvo.customer_total
FROM customers c
JOIN HighValueOrders hvo ON c.id = hvo.customer_id
ORDER BY hvo.customer_total DESC;

Key Takeaways

• CTEs improve query readability by breaking complex logic into clean, named steps.

In Part 82, we compare CTEs vs Derived Tables vs Subqueries!