select count(distinct(device_id)) as did_cnt,count(question_id) as question_cnt from question_practice_detail where date between '2021-08-01' and '2021-08-31'
需要注意device_id 有重复出现，需要在计数的时候使用distinct过滤结果集中的重复数据,between 可以规定8月份的区间未月初到月末