题解 | #21年8月份练题总数#
21年8月份练题总数
https://www.nowcoder.com/practice/b8f30b239b454ed490367b53ea95607d
发现更牛的写法，就是用group by去代替distinct，因为在数据量大的情况下，去重会消耗性能。
select count(temp.did_cnt) as did_cnt, sum(temp.q_cnt) as question_cnt
from(
select
count(1) as did_cnt,
count(question_id) as q_cnt
from
question_practice_detail
where date >= '2021-08-01' and date <= '2021-08-31'
group by device_id
) temp
