题解 | #月均完成试卷数不小于3的用户爱作答的类别#
月均完成试卷数不小于3的用户爱作答的类别
https://www.nowcoder.com/practice/b1d13efcfa0c4ecea517afbdb9090845
# 子查询:选出“当月均完成试卷数” 不小于3的用户 # 按用户、月份分组,选出用户每个月的作答次数 都大于2 的用户 # 外层查询:统计类别及作答次数 select tag, count(1) as tag_cnt from exam_record left join examination_info using (exam_id) where uid in ( select uid from exam_record where submit_time is not null group by uid,DATE_FORMAT (submit_time, "%Y%M") having count(submit_time) > 2 ) group by tag order by tag_cnt desc