数据库系统教程(何玉洁_李宝安_编著)第6章习题参考答案(2)

where exists(

select sno,sum(credit) 'total credit' from SC join course c on SC.cno = c.cno group by SC.sno

having sum(credit) > 3)

17. 查询在第4学期开设课程中与第1学期开设的课程学分相同的课程，列出课

程名和学分。

select cname,credit from course

where semester in (1,4) and credit in(

select credit from course where semester = 4 intersect

select credit from course where semester = 1)

18. 查询“李勇”和“王大力”所选的相同的课程，列出课程名、开课学期和学

分。

select cname,semester,credit from course where cno in(

select cno from SC join student s on SC.sno = s.sno

where sname = '李勇' intersect

select cno from SC join student s on SC.sno = s.sno where sname = '王大力')

19. 查询“李勇”选了但“王大力”没有选的课程，列出课程名、开课学期和学

分。

select cname,semester,credit from course where Cno in(

select cno from SC join student s on SC.sno = s.sno where Sname = '李勇' except

select cno from SC join student s on SC.sno = s.sno where Sname = '王大力')

20. 查询至少同时选了“C001”和“C002”这两门课程的学生的学号和所选的课

程号。

select sno,cno from SC where sno in(

select sno from SC where cno = 'C001' intersect

select sno from SC where cno = 'C002')

*以上内容仅供参考

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