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 
    destination_city,
    transport_name,
    round(sum(timestampdiff(day,order_date,delivery_date))/count(*),2) as  average_transport_duration,
    round(sum(total_cost),2) as total_transport_cost
from transport_detail td inner join order_info oi on td.transport_id = oi.transport_id
inner join cost_data cd on cd.order_id = oi.order_id
group by transport_name,destination_city
order by destination_city asc,transport_name asc;