用户数 根据用户分组 题目总数，？未分组？

select count(did_cnt) , sum(question_cnt) from (select count(device_id) did_cnt,count(question_id) question_cnt from question_practice_detail t where t.date between str_to_date('2021-08-01','%Y-%m-%d') and str_to_date('2021-08-31','%Y-%m-%d') group by device_id) t

group by t.did_cnt

起别名 'Every derived table must have its own alias

稀里糊涂的就过了