根据题意把符合条件的数据先列出来成为新的表格

with e as(
select er.score
from exam_record er
left join examination_info ei
on er.exam_id=ei.exam_id
where ei.tag='SQL'
and er.score is not null
)

再找出所有大于等于平均数的数据，找出最小的分数

with e as(
select er.score
from exam_record er
left join examination_info ei
on er.exam_id=ei.exam_id
where ei.tag='SQL'
and er.score is not null
)
select 
min(score) min_score_over_avg
from e
where score>=(select avg(score) from e)