list the canceled product customer id?
select product_id from customer_orders as t1 join order_items as t2 on t1.order_id = t2.order_id where order_status = 'Cancelled'
which is the order date of customer id 5?
select order_date from customer_orders where customer_id = 5
what the average order quantity for all the order items?
select avg ( order_quantity ) from order_items