题解 | #得分不小于平均分的最低分#

select 
    min(score)
from (
    select 
        score,
        avg(score) over() as average,
        (score - avg(score) over()) as min_score_over_avg
    from (select exam_id, tag from examination_info where tag='SQL') a 
    inner join (select * from exam_record where score is not null) b
    on a.exam_id =b.exam_id ) c
where min_score_over_avg >= 0