题解 | #统计有未完成状态的试卷的未完成数和未完成率#
统计有未完成状态的试卷的未完成数和未完成率
http://www.nowcoder.com/practice/69fc2b1df4144c0991e4b8280d8aba27
select exam_id,sum(if(submit_time is null,1,0)) as incomplete_cnt, round(sum(if(submit_time is null,1,0))/count(1),3) as complete_rate from exam_record group by exam_id having sum(if(submit_time is null,1,0)) > 0