mySql关于统计数量的SQL查询操作

我就废话不多说了，大家还是直接看代码吧~

select project_no,
sum(case when device_state=0 then 1 else 0 end)as offTotal ,
sum(case when device_state=1 then 1 else 0 end)as onlineTotal,
sum(1)total
from iot_d_device
group by project_no
order by project_no