with tb as ( select e1.tag,e2.score,e1.difficulty from examination_info e1 inner join exam_record e2 on e1.exam_id = e2.exam_id and e1.tag = 'SQL' and e1. difficulty='hard' and e2.score is not null ) select tag,difficulty, round((sum(score)-max(score)-min(score))/(count(score)-2),1) as clip_avg_scor...