题解 | 查询出每个运输方式在不同城市的平均运输时长以及总运输费用

select
    distinct 
    destination_city,transport_name,
    round(avg(timestampdiff(day, order_date,delivery_date))
    over(partition by destination_city,transport_id),2)
    as average_transport_duration,
    sum(total_cost) 
     over(partition by destination_city,transport_id)
     as total_transport_cost
from
    order_info
    left join cost_data using (order_id)
    left join transport_detail using(transport_id)