Touge MySQL database - Getting to know MySQL for the first time Answer

Level 1: Create a database

Connect to MySQL on the right command line and create a database named MyDb .

The user name to connect to the database is: root , and the password is: 123123 .

mysql -uroot -p123123 -h127.0.0.1
create database MyDb

Level 2: Creating Tables

Operate in the command line on the right, create the database TestDb , and create the table t_emp under TestDb . The table structure is as follows:

Field Name	type of data	Remark
id	INT	employee ID
name	VARCHAR(32)	employee name
deptId	INT	Department number
salary	FLOAT	salary

mysql -uroot -p123123 -h127.0.0.1
use TestDb
create table t_emp(
    id int,
    name varchar(32),
    deptId int,
    salary float
    );

Level 3: Using primary key constraints

In the database MyDb , create two tables t_user1 and t_user2 . The table structure is as follows. Please create primary key constraints for the two tables respectively. The primary key of t_user1 is userId , the primary key of t_user2 is the joint primary key, and the fields name and phone are used as the joint primary key of t_user2 .

Table t_user1

field name	type of data	Remark
userId	INT	User ID
name	VARCHAR(32)	username
password	VARCHAR(11)	password
phone	VARCHAR(11)	telephone number
email	VARCHAR(32)	Mail

table t_user2

field name	type of data	Remark
name	VARCHAR(32)	username
phone	VARCHAR(11)	telephone number
email	VARCHAR(32)	Mail

create database MyDb
use MyDb
create table t_user1(
userId int primary key,
name varchar(32),
password varchar(11),
phone varchar(11),
email varchar(32)
);
create table t_user2(
name varchar(32),
phone varchar(11),
email varchar(32),
primary key(name,phone)
);

Level 4: Foreign key constraints

创建两张表如下，给t_student表添加外键约束，外键为classId,外键名称为fk_stu_class1。

表t_class

字段名称	数据类型	备注
id	INT	班级Id，主键
name	VARCHAR(22)	班级名称

表t_student

字段名称	数据类型	备注
id	INT	学号，主键
name	VARCHAR(22)	学生姓名
classId	INT	班级ID，外键

在创建表之前你需要先创建数据库：MyDb，并且将两张表创建在MyDb数据库中。

mysql -uroot -p123123 -h127.0.0.1
create database MyDb;//已经创建了的就无需再创建了
use MyDb
create table t_class(
id int primary key,
name varchar(22)
);

create table t_student(
id int primary key,
name varchar(22),
classId int,
constraint fk_stu_class1 foregin key(classId) references t_class(id)
);

第5关：添加常用约束

在数据库MyDb中创建表t_user，表结构如下：

字段名称	数据类型	备注
id	INT	用户ID，主键，自动增长
username	varchar(32)	用户名，非空，唯一
sex	varchar(4)	性别，默认“男”

提示：若要给字段添加两个或者两个以上的约束，约束之间以空格隔开即可。

mysql -uroot -p123123 -h127.0.0.1
create database MyDb;
use MyDb
create table t_user(
id int primary key auto_increment,
username varchar(32) not null unique,
sex varchar(4) default '男'
)default charset = utf8;