user_info 是a,examination_info 是b,exam_record 是c select a.uid, round(avg(if(c.score is null,0,c.score)),0) avg_score, round(avg(if(timestampdiff(minute,start_time,submit_time) is null,b.duration,timestampdiff(minute,start_time,submit_time))),1) avg_time_took from user_info a,examination_info b,exam_r...
