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;

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