ลูกค้าที่ซื้อสินค้ามากที่สุดชื่ออะไร?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
What is the name of the customer that has purchased the most items?It is not neccessary to use all the tables.
 order_items:  order_id [ number]  product_id [ number]  order_quantity [ text] 
SELECT t1.customer_name 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 GROUP BY t1.customer_name ORDER BY SUM(t3.order_quantity) DESC LIMIT 1