เมืองใดมีลูกค้าอาศัยอยู่มากที่สุด?
Which city has the most customers living in?
df_customers = pd.DataFrame(columns=['customer_id']); df_addresses = pd.DataFrame(columns=['city', 'address_id']); df_customer_addresses =  pd.DataFrame(columns=['customer_id', 'address_id'])
df_addresses[df_addresses['address_id'].isin(df_customer_addresses[df_customer_addresses['customer_id'].isin(df_customers['customer_id'])]['address_id'])]['city'].mode()[0]