数据库系统概论第四版-官方第三章讲义中习题答案
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2009-04-23
11:24:13
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1. 元组在某个集合中；
2. 任意字符串，任意一个字符
3. 元组小于集合中所有的元组值
4. D
5. C
6. A
7. ∏
ENO,ENAME
()
8. C
9. A
10. D
11. D
12. A
13. C
14. C
15. C
16. D
17. C
18. D
19. Select max(sage), min(sage) from student where sdept=‘计算机系’
20. Select sname,max(sage) from student where sdept=‘计算机系’
21. Select cno,count(*),max(grade) From sc Group by cno
22. Select sno, sum(grade) from sc group by sno having sum(grade)>200
23. Select c.cno,cname from course c left join sc on c.cno=sc.cno where sc.cno is null
Select cno,cname from course where not exists (select * from sc where sc.cno=course.cno)
24. Select sname,cno,grade From student Where sno in (select sno From sc Where grade>80 order
by grade desc)
25. 1.
（1）
Select Bname, Writer from B where publisher ='人民出版社';
(2)
Select Rname, Bname, Date from R, B, RB
where (R.Rno = RB.Rno AND B.Bno = RB. Bno AND Getdate()>Date);
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