题解 | #0级用户高难度试卷的平均用时和平均得分#
0级用户高难度试卷的平均用时和平均得分
https://www.nowcoder.com/practice/bb474c6cbd77478fb6d9fc86934d0ebb
SELECT ui.uid, round(AVG(COALESCE(er.score, 0)),0) AS avg_score, round(AVG(COALESCE(TIMESTAMPDIFF(minute, er.start_time, er.submit_time), duration)),1) AS avg_time_took FROM user_info ui LEFT JOIN exam_record er ON ui.uid = er.uid LEFT JOIN examination_info ei ON er.exam_id = ei.exam_id WHERE ei.difficulty = 'hard' and ui.level=0 GROUP BY ui.uid;
注意一下COALESCE的用法,别舍近求远了。写 if写得累死了