题解 | #统计作答次数#
统计作答次数
https://www.nowcoder.com/practice/45a87639110841b6950ef6a12d20175f
1. 针对count() 函数具体字段的灵活运用
select count(id) total_pv,
       count(submit_time) complete_pv,
       count(distinct if(submit_time is not null and score is not null,exam_id,null)) complete_exam_cnt
       from exam_record ; 

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