题解 | #某滴出行9月各城市每天的司机数#
某滴出行9月各城市每天的司机数
http://www.nowcoder.com/practice/3487caa8501c4490bbbff25620b88781
select city_name,dt,count(distinct driver_id) as driver_num
from driver_tb d
left join city_tb c
on d.city_id=c.city_id
where month(dt)=9
group by d.city_id,dt;
