Needing Assistance With Counting The Most Different Books

Which customer(s) ordered the most different books? Display the customer id and include ties. This is not talking about the quantity of books ordered. For example, suppose my only

Solution 1:

Try this:

SELECT c.cust_id, COUNT(DISTINCT od.book_id) bookCnt
FROM a_bkorders.customers c 
INNER JOIN a_bkorders.order_headers oh ON c.cust_id = oh.cust_id 
INNER JOIN a_bkorders.order_details od ON oh.order_id = od.order_id 
GROUP BY c.cust_id
ORDER BY bookCnt DESC