A. select a.学号,姓名,count(*) as 选课数,avg(成绩) as 平均分,rank() over(order by avg(成绩) desc) as 排名 from 学生表 a join 选课表 b on a.学号=b.学号 group by a.学号,姓名

B. select a.学号,姓名,count(*) as 选课数,avg(成绩) as 平均分,rank() over(order by avg(成绩) asc) as 排名 from 学生表 a join 选课表 b on a.学号=b.学号 group by a.学号,姓名 having count(*)>=10

C. select a.学号,姓名,count(*) as 选课数,avg(成绩) as 平均分,rank() over(order by avg(成绩) desc) as 排名 from 学生表 a join 选课表 b on a.学号=b.学号 group by a.学号,姓名 having count(*)>=10

D. select a.学号,姓名,count(*) as 选课数,avg(成绩) as 平均分,rank() over(order by avg(成绩) asc) as 排名 from 学生表 a join 选课表 b on a.学号=b.学号 group by a.学号,姓名