题解 | #SQL类别高难度试卷得分的截断平均值#
SQL类别高难度试卷得分的截断平均值
https://www.nowcoder.com/practice/a690f76a718242fd80757115d305be45
select t1.tag, t1.difficulty, round((sum(t2.score)-max(t2.score)-min(t2.score))/(count(t2.score)-2),1) as clip_avg_score from examination_info as t1 join exam_record as t2 on t1.exam_id=t2.exam_id where t1.tag="SQL" and t1.difficulty='hard'
这里要注意一点:
在使用count时:
count(*)会计算空值以及null值.
count(字段名)不会计算null值,但是会计算空值)
，把邮箱都干满了