Lucas Mancini มีคำสั่งซื้อกี่รายการ?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
How many orders does Lucas Mancini has?It is not neccessary to use all the tables.
 invoices:  (customer_id [ VARCHAR) ]
SELECT COUNT(*) FROM customers AS T1 JOIN invoices AS T2 ON T1.id = T2.customer_id WHERE T1.first_name = "Lucas" AND T1.last_name = "Mancini"