Show me the names of all customers who have at least two orders.
select t2.customer_name from orders as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t2.customer_id having count(*) >= 2
Show me the number of orders each of them made as well.
select t2.customer_name, count(*) from orders as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t2.customer_id having count(*) >= 2