1661_average_time_of_process_per_machine

# Write your MySQL query statement below

select
    s.machine_id,
    round(avg(e.timestamp-s.timestamp),3)as processing_time
from Activity s
left join Activity e
on s.machine_id=e.machine_id
and s.process_id=e.process_id
and s.activity_type='start'
and e.activity_type='end'
group by 1