เมืองใดมีลูกค้ามากที่สุด?ไม่จำเป็นต้องใช้ทุกโต๊ะ
Which city does has most number of customers?It is not neccessary to use all the tables.
 Customers:  (customer_address_id [ VARCHAR) ]
SELECT T2.city FROM Customers AS T1 JOIN Addresses AS T2 ON T1.customer_address_id = T2.address_id GROUP BY T2.city ORDER BY COUNT(*) DESC LIMIT 1