题解 | #统计作答次数#
统计作答次数
http://www.nowcoder.com/practice/45a87639110841b6950ef6a12d20175f
select count(id) as total_pv,
sum(if(score is not null, 1, 0)) as complete_pv,
count(distinct if(score is not null, exam_id, null)) as complete_exam_cnt
from exam_record;
