WITH RecentOrders AS (
    SELECT order_id, customer_id, total_amount
    FROM orders
    WHERE order_date >= CURRENT_DATE - INTERVAL '30 days'
),
HighValueCustomers AS (
    SELECT customer_id, SUM(total_amount) AS total_spent
    FROM RecentOrders
    GROUP BY customer_id
    HAVING SUM(total_amount) > 500
)
SELECT c.customer_name, hvc.total_spent
FROM customers c
JOIN HighValueCustomers hvc ON c.customer_id = hvc.customer_id
ORDER BY hvc.total_spent DESC;