Question

查询没有先行课的课程号与课程名(数据库系统概论)

Answer 1

select Cno,Cname from Course where Cpno =''

Answer 2

select a.courseID,a.courseName from courseTable as a where exsits (select b.courseID,count(b.stuID) as ccnum from 选修表 as b where b.ccnum=1 and a.courseID=b.courseID group by b.courseID)