::For nothing can seem foul to those that win::

select Student.StudentId,StudentName,ClassId,(select ClassName from Class where Class.ClassId=Student.ClassId) ClassName,
CASE
 when StudentToCourse.CourseId is  NULL 
  then '未修'
 ELSE '已修' end  选课状态
from  Student
left join StudentToCourse on Student.StudentId=StudentToCourse.StudentId where Student.ClassId='2003050111'

-------------------------------------------------这下大家满足了吧----------------------------------------------------------------------