with
t1 as(
    select
        exp_type,
        avg(timestampdiff(second,out_time,in_time)/3600) as avg_time
    from
        exp_action_tb left join express_tb using(exp_number)
    group by
        exp_type
)

select
    exp_type,
    round(avg_time,1) as time
from
    t1
order by
    time