Question

SQL 这个题怎么做？

a)select avg(price),type from book group by type
B）a)select avg(price),type from book group by price
为什么？

Answer 1

有问题联系我2511837361

--1
select couno,couname from course
where course not in('004','007','013')
--2
select student.stuno,student.stuname from student
inner join stucou on student.stuno=stucou.stuno
inner join course on couse.couno=stucou.couno
--3
select avg(COUNT(student.stuno)) from student
inner join stucou on student.stuno=stucou.stuno
inner join course on couse.couno=stucou.couno
group by kind
--4
select classno,student.stuno,student.stuname,couname,tracher,schooltime from student
inner join stucou on student.stuno=stucou.stuno
inner join course on couse.couno=stucou.couno
inner join class on student.classno=class.classno
where classname='01电子商务'
--5
update course set schooltime='周二晚' from course
inner join stucou on course.cnuno=stucou.cnuno
inner join student on student.stuno=stucou.stuno
inner join class on class.classno=student.classno
where classname='01电子商务'
--6
alter table stucou
add constraint For_stuno foreign key(stuno) references student(stuno)
--7
create view myview
as
select MIN(COUNT(stuno)),MAX(MIN(COUNT(stuno))),AVG(MIN(COUNT(stuno)))
from student inner join class on student.classno=class.classno group by classno