Basic SQL operations

Catalog

form

View ：

---

form

create database test

--  Create student table  Student
create table Student(Sno char(12) primary key,
					 Sname char(8) unique,
					 Age smallint,
					 Sex char(2))
					 
--  Create a student course selection table  Sc
create table Sc(Sno char(12),
				Cno char(4),
				Grade smallint,
				Primary key(Sno,Cno))
				
					 
--  Create a curriculum  Course
create table Course(Cno char(6),
					Cname char(20) not null,
					Teacher char(8))
--  Delete table  Course
drop table Course

-- stay SC In the table , Establish foreign code constraints ,
--Sno It's the outside code , The reference table is Student（sno）;
alter table Sc
add foreign key(Sno) references  Student(Sno)

					 
--  Add column 
alter table Student
add Sdept char(8) not null

--  Delete column 
alter table Student
drop column Age

--  Modify the column 
alter table Student
alter column Sex char(4) not null

--  Add constraints 
alter table Student
add unique(Sex)

--  Delete constraints 
alter table Student
drop constraint UQ__Student__CA1E3C800519C6AF

--  stay student Create about attributes on the table Sno Unique index of 
create unique index Stusno on Student(Sno)

--  Insert data into table 
insert 
into Student 
values ('1', ' Zhang Tian ', ' male ', ' Computer ')

--  see Student List the information 
select * from Student

--  If in student In the table to delete ’202001020101’ This record 
--  Delete column 、 surface   use drop ,  Delete tuples （ Specific information ） use delete
delete
from Student
where Sno = '202001020101' 


--  to Student Table to add  “ Admission time ” Column , The data type is date 
alter table Student
add S_entrance date


--  Change the data type of age from character type to integer type 
alter table Student
alter column Sage int

--  Add constraints 
--  Add the constraint that the student number must take a unique value 
alter table Student
add unique(Sno)

View ：

        Treat the view as a table .

-- Create a view , Count the number of courses selected by each student , The student number is required to be output 、 The number of elective courses 

--  See the table , Easy to insert data 
select * from Student
select * from Sc;

go        --  View name        List name 
create view Num_course(Sno,Num_course)
as
select Sno,COUNT(*)
from Sc
group by Sno
go

--  Before students take courses , There must be a course , This is the function of outer code ！！！
--  Insert courses and two students' elective schedules 
insert
into Course
values ('1','os',' Teacher wang '),
	   ('2','cs',' Miss Liu ')
-- 2 Student No 
insert
into Sc
values ('202001020102','1',80),('202001020102','2',90)
-- 3 Student No 
insert
into Sc
values ('202001020103','1',95)
--  View view 
select * from Num_course



--  Create a student course selection view , The student number is required to be output 、 full name 、 Course name 
go
create view Course_Student( Student number , full name , Course name )
as
select Student.Sno,Sname,Cname
from Student,Sc,Course
where Student.Sno = Sc.Sno and Sc.Cno = Course.Cno
go