mysql 行列转换

select ID
    ,max(case when course='数学' then score end) as '数学'
    ,max(case when course='英语' then score end) as '英语'
    ,max(case when course='法律' then score end) as '法律'
from score_1
group by id;

select id 
    ,'数学' as course
    ,`数学` as score
from score_2
union all 
select id 
    ,'英语' as course
    ,`英语` as score
from score_2
union all 
select id 
    ,'法律' as course
    ,`法律` as score
from score_2