题解 | 统计各岗位员工平均工作时长

关键：计算时间间隔的函数TIMESTAMPDIFF(MINUTE, a.first_clockin, a.last_clockin)

select post,round(avg(TIMESTAMPDIFF(MINUTE, a.first_clockin, a.last_clockin) / 60),3) work_hours
from staff_tb s join attendent_tb a on s.staff_id=a.staff_id
group by post
order by work_hours desc