select tag,difficulty,round((sum(score)-max(score)-min(score))/(count(score)-2),1) from examination_info ei join exam_record er on ei.exam_id=er.exam_id where tag='SQL' and difficulty='hard' round()保留一位小数；平均数总分除以总人数；
select tag,difficulty,round((sum(score)-max(score)-min(score))/(count(score)-2),1) from examination_info ei join exam_record er on ei.exam_id=er.exam_id where tag='SQL' and difficulty='hard' round()保留一位小数；平均数总分除以总人数；
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