What is the name of the customer who has the least policies listed?
select t1.customer_name from customers as t1 join customers_policies as t2 on t1.customer_id = t2.customer_id group by t1.customer_name order by count(*) asc limit 1
How about the most policies listed?
select t1.customer_name from customers as t1 join customers_policies as t2 on t1.customer_id = t2.customer_id group by t1.customer_name order by count(*) desc limit 1