Find the id of the product ordered in each order.
select product_id from order_items
What are the ids of products ordered by the customer named Rodrick Heaney?
select product_id from customers as t1 join customer_orders as t2 on t1.customer_id = t2.customer_id join order_items as t3 on t2.order_id = t3.order_id where t1.customer_name = "Rodrick Heaney"
How many distinct products has he bought?
select count(distinct product_id) from customers as t1 join customer_orders as t2 on t1.customer_id = t2.customer_id join order_items as t3 on t2.order_id = t3.order_id where t1.customer_name = "Rodrick Heaney"