题解 | #21年8月份练题总数#

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