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
https://www.nowcoder.com/practice/69fc2b1df4144c0991e4b8280d8aba27
select
exam_id
,incomplete_cnt
,round(incomplete_cnt/cnt,3) complete_rate
from
(
select
exam_id
,count(start_time) cnt
,sum(if(submit_time is null,1,0)) incomplete_cnt
from exam_record
group by 1
)table1
where incomplete_cnt != 0
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