Summarize Data with Aggregate Functions and GROUP BY

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

How it works: This query demonstrates how to group rows that have the same values in specified columns into a set of summary rows by using the GROUP BY clause. It then applies aggregate functions (COUNT, SUM, AVG) to each group. Here, it calculates the total orders, total amount spent, and average order value for each customer. The HAVING clause filters these groups, showing only customers who have placed more than 5 orders, ordered by their total spending.