大学数据库原理，第四大题答案全要

其实关系代数和关系演算是很麻烦，很抽象的早期代码。参考学习帮助理解数据库运算即可，学会学懂SQL(结构化查询语言，普遍使用)才是王道。你的问题答案代码比较多，我给你总结到文件里了，下载看吧。

1.select s.sname from spj,p,s where spj.sno=s.sno and spj.pno=p.pno

and p.color='red'

2.select spj.jno from spj where sno in

(

select sno from s where s.city<>'tianjin'

)

3. update spj set sno='S3' where

sno='S5' and pno='p6' and jno='j4'

四.

1. select s#,sname from s where age>22 and sex='男'

2. select c# from c where c# not in (select c# from s,sc where s.s#=sc.s# and sname='张平')

3. select sname from s where s# in( select s# from sc where avg(grage)>80)

4. select sname,sex from s,(select s# from sc where count(s#)>2) t

where t.s#=t.s#

五、

1.

create view v-ssc(

select s.sno,s.sname,sc.cno,sc.grade from s,sc

where s.sno=sc.sno

order by s.sno

)

2.

select sname,cno,grade from v_ssc a

where (select avg(GRADE) from v_ssc b a.sno=b.sno)>90

六、

1.select 图书名，max(定价) from 图书,图书发行

where 图书.图书编号=图书发行.图书编号

2.发行"数据库系统基础"的出版社名字