【Sql Server】Sql语句整理

use Person



<--添加约束-->

Alter table Student

    alter column  Sno char(5) not null;

Alter table Student

    Add constraint uq_sno unique(Sno);

Alter table Student 

    Add constraint C_sex check(Ssex in('男','女'));

Alter table Student 

    Add constraint df_Sage Default 20 for Sage;

Alter table Student 

    Add constraint PK_Sno primary key(Sno);

<--要把字段设置为非空，sqlserver不允许空值列建立主键约束-->

Alter table Course

    alter column Cno char(3) not null

Alter table Course 

    Add constraint PK_Cno primary key(Cno),constraint FK_Cpno_ foreign key(Cpno) references Course(Cno);

Alter table Course

    Drop constraint FK_Cpno_;



Alter table SC

    alter column Cno char(3) not null



Alter table SC

    alter column Sno char(5) not null

Alter table SC

    Add constraint PK_sc primary key(Sno,Cno),constraint FK_Sno foreign key(Sno) references Student(Sno),constraint FK_Cno foreign key(Cno) references Course(Cno)



    

<--插入数据-->

insert into Student(Sno,Sname,Ssex,Sage,Sdept) values('08001','张力','男','18','cs');

select * from Course    

select Getdate()







create table Student

(

    Sno char(5),//学号

    Sname char(20),//姓名

    Ssex char(2),//性别

    Sage Smallint,//年龄

    Sdept  char(15)//系别

); 

create table Course

(

    Cno char(3),//课程号

    Cname char(30),//课程名

    Cpno char(3),//先修课号

    Ccredit Smallint//学分

);



create table SC

(

    Sno char(5),//学号

    Cno char(3),//课程号

    Grade  int//分数

)



                                        <--查询语句-->



select Sno,Grade from SC where Cno='002' order by Grade desc;



select * from SC ORDER BY Cno,Sno desc;



select count(distinct Sno) from Student



select AVG(Grade) from SC where Cno='002';

select max(grade) from SC where Cno='001'



select Sdept,count(Sno) from Student Group by Sdept;



select Cno,avg(Grade) from SC group by Cno;



select Sno,avg(Grade) from SC group by Sno;

<--查询选修了3门课程以上的学生的学号-->

select Sno,Count(Cno) from SC group by Sno having count(cno)>3 ;

<-查询所有成绩为优秀的学生的学号->

select Sno,min(grade) 

from SC 

where Sno 

    not in(select Sno from SC where Grade is null) 

    Group by Sno 

    having min(Grade)>=90;



<--等值连接:查询每个学生及其选修课程的情况-->

select Student.*,Sc.* 

from Student,Sc 

where Student.Sno=Sc.Sno;



select Sno,Cno from Student,Course;

<--自身连接查询:查询每门课程的见解先修课-->

select First.Cno,Second.Cpno 

from Course as First,Course as Second 

where First.Cpno=Second.Cno;



<--自身连接查询:查询和刘晨在同一个系的学生-->

Select S2.* from Student S1,Student S2 

where S1.Sname='刘晨' And S1.Sdept=S2.Sdept;



<--外连接查询->

Select Student.*,Sc.* from Student Left Join Sc On Student.Sno=Sc.Sno;



<--复合连接查询:查询选修了002课程号且成绩大于90的学生情况-->

select student.* from Student,Sc 

where Student.Sno=SC.Sno And Sc.Cno='002' And Grade>'90';



<--复合连接查询:查询选修了课程的学生姓名、课程名、和成绩-->

Select Sname,Cname,Grade 

from Student,SC,Course 

where Student.Sno=SC.Sno And 

      Sc.Cno=Course.Cno;



<--查询所有成绩为优秀的学生姓名-->

Select Sname 

from Student,Sc 

where Student.Sno=SC.Sno And 

      Student.Sno Not in(Select Sno from SC where Grade is null) 

      group by Sname 

      having min(Grade)>80;



<--子查询:查询未被学生选修的课程信息--->

select * from Course where Course.Cno not in (select Distinct Cno from Sc)



<--子查询:查询选修了课程名为数据库的课程的学生信息-->



select Cno from Couse where Cname='数据库'



select Sno from Sc 

where Cno 

in(select Cno from Couse where Cname='数据库')



select * from Student 

where Sno in(select Sno from Sc where Cno in(select Cno from Course where Cname='数据库'));



select Student.* from Student,SC,Course 

where Student.Sno=SC.Sno 

      And Sc.Cno=Course.Cno 

      and Course.Cname='数据库';

      

<--子查询:查找其它系中比IS某一系学生年龄小的学生信息-->

select * from Student 

where Sage< Any(select Sage from Student where Sdept='is') 

      And Sdept<>'is' Order by Sage Desc;



<--相关子查询：查询比本系平均年龄大的的学生信息-->

select * 

from Student S1

where Sage>

        (select avg(Sage)

        from Student S2 where S1.Sdept=S2.Sdept)



<--Exists子查询；查询所有选修了001号课程的学生姓名-->

select Sname

from Student

where Exists(select *

            from Sc where Sno=Student.Sno And Cno='001');

                    





                                                <--集合查询-->

<--UNION运算符：查询计算机系的学生以及年龄不大于19的学生-->

Select * from Student where Sdept='CS'

Union

Select * from Student where Sage<=19;



Select * 

from Student 

where Sdept='Cs' Or Sage<=19;



<--集合的交操作 Intersect:查询选修了课程001而且002的学生学号-->

select Sno from Sc 

where Cno='001' And Sno In

                    (Select Sno From Sc where Cno='002');    



Select A.Sno from Sc A,Sc B

where A.Cno='001' And B.Cno='002' And A.Sno=B.Sno;            

                                    

                                                <--插入数据-->

<--创建新表Deptage，保存每一个系的学生平均年龄-->

Create table Deptage

(

    Sdept Char(15),

    Avgage Smallint

)

<--对Student表按系别进行分组，求平均年龄，然后存入表Deptage-->

Insert into 

Deptage(Sdept,Avgage) select Sdept,avg(Sage) 

from Student group by Sdept;









                                                <--修改数据-->

<--把选修了课程名为'数据库'的课程的学生的成绩改为0-->

Update Sc set Grade=0 where Cno in(Select cno 

        from Course 

        where Cname='数据库')

        

        

                                                <--删除数据-->

<--删除所有学生的选课记录-->

delete from sc;

<--删除计算机系(cs)所有学生的选课记录-->

delete 

from SC 

where Sno in(select Sno 

                    from Student 

                    where Sdept='CS')

                    

delete 

from SC 

where 'CS'=(select Sdept

                    from Student

                    where Student.Sno=Sc.Sno)