题解 | 统计各岗位员工平均工作时长

select  a.post,round(avg((UNIX_TIMESTAMP(last_clockin) - UNIX_TIMESTAMP(first_clockin)) / 3600),3)
work_hours from staff_tb a 
join attendent_tb b using(staff_id)
where b.first_clockin is not null and b.last_clockin is not null
group by a.post order by  work_hours desc

UNIX_TIMESTAMP(last_clockin) - UNIX_TIMESTAMP(first_clockin)) / 3600 计算精确到秒的日期差，/3600为小时差 /60 为分钟差