sql server 基础语法4 实践练习+子查询

drop table class
create table class (
    classId nchar(6) primary key not null,
    cName nvarchar(20)
)
insert into class
values('09033','自动化1班')
insert into class
values('09031','计算机1班'),
('09032','计算机2班'),
('09034','自动化2班')

select * from class

delete class where classId='09033'
delete class where classId='09031'
delete class where classId='09032'
delete class where classId='09034'


update class set cName='自动化3班'
where classId=09034

alter table student 
alter column classId nchar(6)not null

alter table student --给student的classId属性增加一个外键
add constraint classId foreign key(classId) references class(classId)
 
alter table student --删掉该外键约束
drop constraint classId 

--然后才能删掉class
drop table class

select * from course
select * from score
select * from student
select * from teacher

--检查学号为107的学生的课程名，任课老师
select ci.cName,ti.teaName from student as si 
inner join score as sco on sco.stuId=si.stuId
inner join course as ci on ci.cId=sco.cId
inner join teacher as ti on ti.teaId=ci.teaId
where si.stuId=107

--检索王同学不学习且不助教的任课老师和课程名
select ti.teaName,ci.cName from course as ci
inner join teacher as ti on ti.teaId=ci.teaId
except (
--王同学学习的课程及任课老师
select ti.teaName,ci.cName from student as si
inner join score as sco on sco.stuId=si.stuId
inner join course as ci on ci.cId=sco.cId
inner join teacher as ti on ci.teaId=ti.teaId
where si.stuName like '王%'
union 
--王同学助教的任课老师的课
select ti.teaName,ci.cName from course as ci
inner join teacher as ti on ci.teaId=ti.teaId
where ti.teaWork='助教' and ti.teaName like '王%'
)

--检索至少选修两门课程的学生学号
select sco.stuId,COUNT(*) from score as sco
group by sco.stuId having COUNT(*)>1


--子查询
--按学号列出每个学生所选修课程中最高分的课程名称及其分数
select si.stuId,ci.cName,sco.score 
from student as si
inner join score as sco on sco.stuId=si.stuId
inner join course as ci on ci.cId=sco.cId
inner join teacher as ti on ci.teaId=ti.teaId
where sco.score>=
(
    select MAX(ssco.score) from student as ssi
    inner join score as ssco on ssco.stuId=ssi.stuId
    inner join course as cci on cci.cId=ssco.cId
    inner join teacher as tti on cci.teaId=tti.teaId
    where ssi.stuName=si.stuName
)
order by si.stuId asc