Aggregate Data with GROUP BY and Filter Groups with HAVING

SELECT
  customer_id,
  COUNT(order_id) AS total_orders,
  SUM(total_amount) AS total_spent
FROM
  orders
GROUP BY
  customer_id
HAVING
  COUNT(order_id) > 5 AND SUM(total_amount) > 1000
ORDER BY
  total_spent DESC;

How it works: This query aggregates order data by `customer_id`, calculating the total number of orders and total amount spent for each customer. The `GROUP BY` clause groups rows with the same `customer_id`. The `HAVING` clause then filters these *groups* based on aggregate conditions, showing only customers who have placed more than 5 orders and spent over 1000 units. This is essential for identifying high-value customers or analyzing customer segments.