Database experiment I: data definition experiment guide

Experiment 1 Data definition and experimental guidance

（ Database schema design and establishment ）

1． The experiment purpose

（1） Let students complete the design of database schema by themselves .

（2） use SQL Command to create database tables .

（3） Create database tables with visual environment .

2． Experimental content

（1） Define data table .

（2） Modify table structure ： Add field , Modify field type .

（3） Delete table structure .

3． The experimental requirements

（1） Establish student database mode .

 Student list ：student  (sno,  sname,  ssex,  sage,  sdept)

    Student     Student number    full name     Gender     Age   Department 

 sno     The length is 4 String 

sname   The length is 8 String 

ssex     The length is 2 String 

sage     Short integer 

sdept    The length is 10 String 

 among sno Main code .

CREATE TABLE IF NOT EXISTS student(

	sno VARCHAR(4) NOT NULL PRIMARY KEY COMMENT ' Student number , Primary key ',
	
	sname VARCHAR(8) NOT NULL COMMENT ' full name ',
	
	ssex VARCHAR(2) NOT NULL COMMENT ' Gender ',
	
	sage TINYINT(3) UNSIGNED DEFAULT 0 COMMENT ' Age ',
	
	sdept VARCHAR(10) NOT NULL COMMENT ' Department '

)ENGINE=InnoDB CHARSET=UTF8 COMMENT=' Student list ';

 The curriculum ：course  (  cno,  cname)
 Course     Course no.    Course name     credits 
 
cno      The length is 4 String 

cname    The length is 10 String 

credit    Short integer 

 among cno Main code .

CREATE TABLE IF NOT EXISTS course(

	cno VARCHAR(4) NOT NULL PRIMARY KEY COMMENT ' Course no. , Primary key ',
	
	cname VARCHAR(10) NOT NULL COMMENT ' Course name ',
	
	credit TINYINT(3) UNSIGNED DEFAULT 0 COMMENT ' credits '

)ENGINE=InnoDB CHARSET=UTF8 COMMENT=' The curriculum ';

 Course selection table ： sc   (sno,    cno,  cname,  grade)

 Course selection    Student number     Course no.    Course name     achievement 

sno   The length is 4 String 

cno   The length is 4 String 

cname   The length is 10 String 

grade   Short integer 

 among (sno, cno)  Main code ;sno For outer code and student Table correspondence ;cno For outer code and course Table correspondence ;
 grade The value of is either empty or 0—100 Between .

CREATE TABLE sc(

	sno VARCHAR(4),
	
	cno VARCHAR(4),
	
	cname VARCHAR(10),
	
	grade INT CHECK(grade BETWEEN 0 AND 100),
	
	PRIMARY KEY (sno,cno),
	
	FOREIGN KEY (sno) REFERENCES student(sno) ON DELETE CASCADE,
	
	FOREIGN KEY (cno) REFERENCES course(cno)

)ENGINE=InnoDB CHARSET=UTF8;

（2） Modify data table structure

 Add a... To the curriculum credit Field , Indicates credits , The type is short .

 Delete... From the course selection list cname Field .

ALTER TABLE course MODIFY credit TINYINT COMMENT ' credits ';

ALTER TABLE sc drop cname;

（3） Undo data table . Create a temporary table , Then undo it .

CREATE TABLE TEMP(

	cno VARCHAR(4) PRIMARY KEY,
	
	cname VARCHAR(10),
	
	credit TINYINT

);

DROP TABLE temp;

Ask to write all the code of Experiment 1 ,
Be careful ：
1. All the code
2. The full width of the code
3. Regular format , Easy to read