select
    er.exam_id,
    count(distinct er.uid) as uv,
    round(avg(score),1) as avg_score
from
    user_info as ui
    inner join
    exam_record as er
    on
    ui.uid=er.uid
    inner join
    examination_info as ei
    on
    er.exam_id=ei.exam_id
where
    ei.tag='SQL'
    and
    date_format(ei.release_time,'%Y-%m-%d')=date_format(er.submit_time,'%Y-%m-%d')
    and
    ui.level>5
group by
    ei.exam_id
order by
    uv desc,
    avg_score asc