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)) incomplete_cnt, round(sum(if(submit_time is null,1,0)) / count(start_time),3) incomplete_rate
from exam_record
group by exam_id
having incomplete_cnt>0;
from exam_record
group by exam_id
having incomplete_cnt>0;
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