Which customer id filed the least number of complaints? How many?
select customer_id, count(*) from complaints group by customer_id order by count(*) asc limit 1
Which product names did this customer complain about?
select distinct t1.product_name from products as t1 join complaints as t2 on t1.product_id = t2.product_id join customers as t3 group by t3.customer_id order by count(*) limit 1