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(
        avg(timestampdiff(day, order_date, delivery_date)),
        2
    ) as average_transport_duration,
    round(sum(total_cost),2) as total_transport_cost
from
    transport_detail as t
    inner join order_info as o on t.transport_id = o.transport_id
    inner join cost_data as c on o.order_id = c.order_id
group by
    destination_city,
    transport_name
order by
    destination_city asc,
    transport_name asc;