1. 关系型数据库介绍

1.1 数据结构模型

数据结构模型主要有：

• 层次模型
• 网状结构
• 关系模型

关系模型：
二维关系：row，column

数据库管理系统：DBMS
关系：Relational，RDBMS

1.2 RDBMS专业名词

常见的关系型数据库管理系统：

• MySQL：MySQL，MariaDB，Percona-Server
• PostgreSQL：简称为pgsql
• Oracle
• MSSQL

SQL：Structure Query Language，结构化查询语言

约束：constraint，向数据表提供的数据要遵守的限制

• 主键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。且必须提供数据，不能为空（NOT NULL）。
  • 一个表只能存在一个
• 惟一键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。允许为空（NULL）
  • 一个表可以存在多个
• 外键约束：一个表中的某字段可填入数据取决于另一个表的主键已有的数据
• 检查性约束

索引：将表中的一个或多个字段中的数据复制一份另存，并且这些数据需要按特定次序排序存储

1.3 关系型数据库的常见组件

关系型数据库的常见组件有：

• 数据库：database
• 表：table，由行（row）和列（column）组成
• 索引：index
• 视图：view
• 用户：user
• 权限：privilege
• 存储过程：procedure
• 存储函数：function
• 触发器：trigger
• 事件调度器：event scheduler

1.4 SQL语句

SQL语句有三种类型：

• DDL：Data Defination Language，数据定义语言
• DML：Data Manipulation Language，数据操纵语言
• DCL：Data Control Language，数据控制语言

2. mysql安装与配置

2.1 mysql安装

mysql安装方式有三种：

• 源代码：编译安装
• 二进制格式的程序包：展开至特定路径，并经过简单配置后即可使用
• 程序包管理器管理的程序包：
  • rpm：有两种
    • OS Vendor：操作系统发行商提供的
    • 项目官方提供的
  • deb

安装mariadb，设置开机自启动并现在就启动。确保3306端口已经监听起来。

[root@test ~]# yum -y install mariadb*

[root@test ~]# systemctl enable --now mariadb

[root@test ~]# ss -antl
State     Recv-Q     Send-Q          Local Address:Port          Peer Address:Port     
LISTEN    0          128                   0.0.0.0:22                 0.0.0.0:*        
LISTEN    0          80                    0.0.0.0:3306               0.0.0.0:*        
LISTEN    0          128                      [::]:22                    [::]:*  

给mysql设置登录密码为123

[root@win10 ~]# mysql -uroot -p 
Enter password: 
Welcome to the MariaDB monitor. Commands end with ; or \g. 
Your MariaDB connection id is 8 
Server version: 10.3.17-MariaDB MariaDB Server 
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]> set password = password(‘123‘); #后面的password是加密 
Query OK, 0 rows affected (0.000 sec)

修改mysql登录密码

[root@test ~]# mysql -uroot -p123
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 21
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]> alter user ‘root‘@‘localhost‘ identified by ‘123456‘;
Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> quit
Bye
[root@test ~]# mysql -uroot -p123456
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 22
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
MariaDB [(none)]> 

mysql_secure_installation //安全初始化

[root@test ~]# mysql_secure_installation 

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MariaDB to secure it, we‘ll need the current
password for the root user.  If you‘ve just installed MariaDB, and
you haven‘t set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):   输入root账户的密码

Change the root password? [Y/n]  y  是否改变root密码
New password: 
Re-enter new password: 
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] y  要不要移除匿名账户
 ... Success!

Normally, root should only be allowed to connect from ‘localhost‘.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] n 要不要设置不允许root账户远程登陆
 ... skipping.

By default, MariaDB comes with a database named ‘test‘ that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] y 要不要移除测试数据库和访问它的权限
- Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y 要不要重新加入权限表
 ... Success!

Cleaning up...

All done!  If you‘ve completed all of the above steps, your MariaDB
installation should now be secure.

Thanks for using MariaDB!

两种查看数据库的方法

[root@test ~]# mysql -uroot -p123123
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 32
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]>  show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.004 sec)

MariaDB [(none)]> quit
Bye
.................................................................

[root@test ~]#  mysql -uroot -p123123 -e ‘show databases;‘
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+

DDL操作

创建数据库

MariaDB [(none)]> CREATE DATABASE IF NOT EXISTS school;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
+--------------------+
4 rows in set (0.000 sec)

MariaDB [(none)]> 

删除数据库

MariaDB [(none)]> DROP DATABASE IF EXISTS school;
Query OK, 0 rows affected (0.005 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.000 sec)

MariaDB [(none)]> 

表操作

创建一个空表

MariaDB [(none)]> CREATE DATABASE IF NOT EXISTS school;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> use school;
Database changed
MariaDB [school]> show tables;
Empty set (0.000 sec)

MariaDB [school]> CREATE TABLE student(id int not null,name varchar(50)null,age tinyint );
Query OK, 0 rows affected (0.004 sec)

MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student          |
+------------------+
1 row in set (0.000 sec)

MariaDB [school]> 

查看表的结构

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.002 sec)

MariaDB [school]> 

获取创建表的帮助

MariaDB [school]> help create table;
Name: ‘CREATE TABLE‘
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    select_statement

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    { LIKE old_tbl_name | (LIKE old_tbl_name) }

create_definition:
    col_name column_definition
  | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...)
      [index_option] ...
  | {INDEX|KEY} [index_name] [index_type] (index_col_name,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY]
      [index_name] [index_type] (index_col_name,...)
      [index_option] ...
  | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] FOREIGN KEY
      [index_name] (index_col_name,...) reference_definition
  | CHECK (expr)

column_definition:
    data_type [NOT NULL | NULL] [DEFAULT default_value]
      [AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
      [COMMENT ‘string‘]
      [COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
      [STORAGE {DISK|MEMORY|DEFAULT}]
      [reference_definition]
...
...
...

修改表，加入班级class

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.001 sec)

MariaDB [school]> ALTER TABLE student ADD class varchar(20);
Query OK, 0 rows affected (0.004 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> desc student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.002 sec)

删除age

MariaDB [school]> ALTER TABLE student DROP age;
Query OK, 0 rows affected (0.009 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> desc student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.001 sec)

MariaDB [school]> 

删除表

MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student          |
+------------------+
1 row in set (0.000 sec)

MariaDB [school]> DROP TABLE student;
Query OK, 0 rows affected (0.003 sec)

MariaDB [school]> show tables;
Empty set (0.000 sec)

MariaDB [school]> 

DML操作

DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。

MariaDB [school]> DESC student;          查看表的结构
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.003 sec)

MariaDB [school]> ALTER TABLE student ADD class varchar(20);
Query OK, 0 rows affected (0.005 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.001 sec)

增操作insert

MariaDB [school]>                         在表里面加入数据
MariaDB [school]> INSERT INTO student (id,name,age,class) VALUE (1,‘taochi‘,5,5),(2,‘chensongling‘,20,6),(3,‘wangming‘,21,5),(4,‘fangxinxin‘,18,7);
Query OK, 4 rows affected (0.007 sec)
Records: 4  Duplicates: 0  Warnings: 0