select 
    count(distinct device_id) as did_cnt,
    count(question_id) as question_cnt
 #练习过题目的总次数包括 同一/不同 用户对 同一/不同 题目的练习次数，所以每条数据都不能舍去
from question_practice_detail
where date between "2021-08-01" and "2021-08-31"