题解 | #计算用户8月每天的练题数量#

#使用sql中的substring_index字符串截取函数
SELECT SUBSTRING_INDEX(date,"-",-1) as day,
    count(question_id) as question_cnt
from question_practice_detail
where SUBSTRING_INDEX(SUBSTRING_INDEX(date,"-",2),"-",-1)="08"
    group by day;