数据库第三章作业

数据库第六版答案

班级:软件工程2班

姓名:方添翼

学号:2012551523

3.1

A.select * from course where dept_name='Comp. Sci.' and credits=3

B.select distinct student.ID

from (student join takes using(ID))

join (instructor join teaches using(ID))

using(course_id,sec_id,semester,year)

where http://www.wendangwang.com='Einstein'

C.select max(salary) from instructor

D.select http://www.wendangwang.com from instructor a where salary=(select

max(salary)from instructor )

E.select course_id,sec_id,count(ID)

from section natural join takes

where semester='Autumn' and year=2009

group by course_id,sec_id;

F.select max(a)

from (select count(id) as a

from takes natural join section

where semester='Autumn'

and year=2009

group by course_id,sec_id)

G.

3.2

A.(select sum(credits*points)

from (takes natural join course) natural join grade points where ID='12345')

B.select sum(credits*points)/sum(credits) as GPA

from (takes natural join course)natural join grade_points where id='12345'

C.select id,sum(credits*points)/sum(credits) as GPA

from (takes natural join course)natural join grade_points group by id

3.3

A.update instructor

set salary=salary*1.1

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