select score min_score_over_avg from exam_record a,
examination_info b
where 
a.exam_id= b.exam_id 
and tag='SQL'
and a.score>=(select avg(score) from exam_record c,
examination_info d
where c.exam_id= d.exam_id and tag='SQL' )
and a.score is not null
order by a.score asc
limit 1