2-10.sql

一个数据库的选课系统

select distinct student
from   enrolls,teachers,sections
where  exists
      (select *
       from enrolls,teachers,sections
       where teachers.teacher=sections.teacher and sections.course=enrolls.course and teachers.teachername='Dr.Lowe'
       group by student
       having count(distinct enrolls.course)=(select count(distinct enrolls.course)
                                   from enrolls,teachers,sections
                                   where teachers.teacher=sections.teacher and sections.course=enrolls.course and teachers.teachername='Dr.Lowe')
)