v1 思路：当score>avg_score

v1 结果错误。原因：子查询不止一行，而是每个job一行avg_score

select *
from grade
where score > (
    select avg(score) as avg_score
    from grade 
    group by job
)
order by id asc

v2 思路：聚合表，增加一列avg_score。对比score>avg_score

v2结果成功

select 
    g1.*
from grade g1
    left join (
        select job,avg(score) as avg_score
        from grade 
        group by job
    )g2
    on g1.job=g2.job
where g1.score > g2.avg_score