Show the names of all customers.
select customer_name from customers
Also show the number of orders each of them has.
select t1.customer_name, count(*) from customers as t1 join customer_orders as t2 on t1.customer_id = t2.customer_id group by t1.customer_id
Sort the names in descending order of the number of orders.
select t1.customer_name from customers as t1 join customer_orders as t2 on t1.customer_id = t2.customer_id group by t1.customer_id order by count(*) desc
Who has the most?
select t1.customer_name from customers as t1 join customer_orders as t2 on t1.customer_id = t2.customer_id group by t1.customer_id order by count(*) desc limit 1