1.将grade_info表按照用户分数求和 select user_id,sum(grade_num) grades from grade_info group by user_id; t2 2.与user表关联 select id,name,grades from t2 join user t1 on t1.id = t2.user_id; t3 3.给出排序(利用窗口函数) select id,name,grades,rank() over(order by grades desc) rk from t3;t4 4.输出最高 select id,name,grades from...