เมืองไหนมีลูกค้ามากที่สุด?ไม่จำเป็นที่จะต้องใช้โต๊ะทั้งหมด
What is the city with the most customers?It is not neccessary to use all the tables.
 staff:  staff_id [ number]  staff_address_id [ number]  nickname [ text]  first_name [ text]  middle_name [ text]  last_name [ text]  date_of_birth [ time]  date_joined_staff [ time]  date_left_staff [ time] 
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