Customer Spending in MySQL

 

SELECT c.customer_name, ROUND(SUM(i.total_price), 6)

FROM customer c

INNER JOIN invoice i ON c.id=i.customer_id

GROUP BY c.customer_name

HAVING SUM(i.total_price)<0.25*(SELECT AVG(total_price) FROM invoice)

ORDER BY ROUND(SUM(i.total_price), 6) DESC