题解 | #未完成试卷数大于1的有效用户#

不使用if 或 case when 函数的解法： select uid, count(*)-count(submit_time) incomplete_cnt, count(submit_time) complete_cnt, group_concat(distinct concat_ws(':', date(start_time), tag) SEPARATOR ';') as detail from exam_record er inner join examination_info ei on er.exam_id = ei.exam_id where year(start_time) = 2021 group by uid having complete_cnt >=1 and incomplete_cnt >1 and incomplete_cnt <5 order by incomplete_cnt desc