题目：
在SQL Server 数据库中，有一个表StudentAchievement（学生成绩）,它有三个字段：StudentID(varchar(8),学生编号)，CourseID(varchar(10),课程编号)，Achievement(int ，成绩)，写一条SQL语句，筛选出每门课程的前两名的学生编号，课程编号，成绩并排序
答案：
select a.* from StudentAchievement a where a.StudentID in (select top 2 StudentID from StudentAchievement where CourseID=a.CourseID order by Achievement desc)
答案：
select a.* from StudentAchievement a where a.StudentID in (select top 2 StudentID from StudentAchievement where CourseID=a.CourseID order by Achievement desc)
