1.映射出合并后的数据的表
2.映射出最大的分数表
3.按照要求最大的分数筛选出合理的数据
with t1 as (select * ,sum(grade_num) NUM from grade_info JOIN user ON user_id=id GROUP by user_id ),
t2 as( select max(num) mx FROM t1 )
select user_id,name,num from t1 ,t2 where num =t2.mx