题解 | 统计各岗位员工平均工作时长

# timestampdiff(unit,begin,end)
select post, avg(timestampdiff(minute, first_clockin, last_clockin)/60) work_hours
from staff_tb a
inner join attendent_tb b
on a.staff_id = b.staff_id
group by post
order by work_hours desc;