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
SQL语句类型对应操作
DDLCREATE：创建 DROP：删除 ALTER：修改
DMLINSERT：向表中插入数据 DELETE：删除表中数据 UPDATE：更新表中数据 SELECT：查询表中数据
DCLGRANT：授权 REVOKE：移除授权

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
[root@localhost yum.repos.d]# yum -y install mariadb mariadb-server
Updating Subscription Management repositories.
Unable to read consumer identity
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
上次元数据过期检查：0:09:08 前，执行于 2021年08月23日 星期一 20时57分49秒。
依赖关系解决。
===============================================================================================================
 软件包                          架构        版本                                         仓库            大小
===============================================================================================================
安装:
 mariadb                         x86_64      3:10.3.28-1.module_el8.3.0+757+d382997d      AppStream      6.0 M
 mariadb-server                  x86_64      3:10.3.28-1.module_el8.3.0+757+d382997d      AppStream       16 M
安装依赖关系:
 mariadb-common                  x86_64      3:10.3.28-1.module_el8.3.0+757+d382997d      AppStream       64 k
 mariadb-connector-c             x86_64      3.1.11-2.el8_3                               AppStream      200 k
 mariadb-connector-c-config      noarch      3.1.11-2.el8_3                               AppStream       15 k
 mariadb-errmsg                  x86_64      3:10.3.28-1.module_el8.3.0+757+d382997d      AppStream      234 k
 perl-Carp                       noarch      1.42-396.el8                                 base            30 k
 perl-DBD-MySQL                  x86_64      4.046-3.module_el8.1.0+203+e45423dc          AppStream      156 k
......

2.2 mariadb配置

#启动mysql并设置开机自动启动
systemctl enable --now mariadb
systemctl status mariadb

[root@localhost etc]# systemctl enable --now mariadb
Created symlink /etc/systemd/system/mysql.service → /usr/lib/systemd/system/mariadb.service.
Created symlink /etc/systemd/system/mysqld.service → /usr/lib/systemd/system/mariadb.service.
Created symlink /etc/systemd/system/multi-user.target.wants/mariadb.service → /usr/lib/systemd/system/mariadb.service.

[root@localhost etc]# systemctl status mariadb
● mariadb.service - MariaDB 10.3 database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2021-08-23 21:09:47 CST; 2min 7s ago
     Docs: man:mysqld(8)
           https://mariadb.com/kb/en/library/systemd/
 Main PID: 62683 (mysqld)
   Status: "Taking your SQL requests now..."
    Tasks: 30 (limit: 23790)
   Memory: 85.4M
   CGroup: /system.slice/mariadb.service
           └─62683 /usr/libexec/mysqld --basedir=/usr


#确保3306端口已经监听起来
ss -antl
[root@localhost etc]# 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                                 *:3306                            *:*           
LISTEN        0             128                             [::]:22                           [::]:*           

#在日志文件中找出临时密码
grep "password" /var/log/mysqld.log

#使用获取到的临时密码登录mysql
[root@localhost etc]# mysql -uroot -p
Enter password:     //此处输入密码   默认无密码
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 8
Server version: 10.3.28-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)]> exit         //看到有这样的标识符则表示成功登录了
Bye





//修改mysql登录密码
MariaDB [(none)]> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [mysql]> ALTER USER 'root'@'localhost' IDENTIFIED BY '123';
Query OK, 0 rows affected (0.000 sec)
//用新密码登陆测试
[root@localhost etc]# mysql -uroot -p123
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 11
Server version: 10.3.28-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)]>

3. mysql的程序组成

  • 客户端
    • mysql：CLI交互式客户端程序
    • mysql_secure_installation：安全初始化，强烈建议安装完以后执行此命令
    • mysqldump：mysql备份工具
    • mysqladmin
  • 服务器端
    • mysqld

3.1 mysql工具使用

//语法：mysql [OPTIONS] [database]
//常用的OPTIONS：
    -uUSERNAME      //指定用户名，默认为root
    -hHOST          //指定服务器主机，默认为localhost，推荐使用ip地址
    -pPASSWORD      //指定用户的密码
    -P#             //指定数据库监听的端口，这里的#需用实际的端口号代替，如-P3307
    -V              //查看当前使用的mysql版本
    -e          //不登录mysql执行sql语句后退出，常用于脚本
    

[root@localhost etc]# mysql -V
mysql  Ver 15.1 Distrib 10.3.28-MariaDB, for Linux (x86_64) using readline 5.1



[root@localhost etc]# mysql -uroot -p123 -h127.0.0.1
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 13
Server version: 10.3.28-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)]> 

//注意，不推荐直接在命令行里直接用-pPASSWORD的方式登录，而是使用-p选项，然后交互式输入密码
[root@localhost etc]# mysql -uroot -p -h127.0.0.1
Enter password:    //输入密码
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 15
Server version: 10.3.28-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)]> 

不进入数据库查看表
[root@localhost etc]# mysql -uroot -p -h 127.0.0.1 -e 'SHOW DATABASES;'
Enter password:   //输入密码
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+

3.2 服务器监听的两种socket地址

socket类型说明
ip socket默认监听在tcp的3306端口，支持远程通信
unix sock监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock） 仅支持本地通信 server地址只能是：localhost，127.0.0.1

4. mysql数据库操作

4.1 DDL操作

4.1.1 数据库操作
//创建数据库
//语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME';
//创建数据库zxc
MariaDB [(none)]> create database  zxc;
Query OK, 1 row affected (0.000 sec)



//查看当前实例有哪些数据库
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| zxc                |
+--------------------+
4 rows in set (0.000 sec)



//删除数据库
//语法：DROP DATABASE [IF EXISTS] 'DB_NAME';
//删除数据库zxc
MariaDB [(none)]> drop database  zxc;
Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.000 sec)
4.1.2 表操作
//创建表
//语法：CREATE TABLE table_name (col1 datatype 修饰符,col2 datatype 修饰符) ENGINE='存储引擎类型';
//在数据库zxc里创建表asd
MariaDB [(none)]> create database zxc;     //创建数据库zxc
Query OK, 1 row affected (0.000 sec)

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


MariaDB [(none)]> use zxc;   //使用数据库zxc
Database changed
MariaDB [zxc]> create table asd(id int(7) ,name varchar(5) not null );    //创建表asd
Query OK, 0 rows affected (0.003 sec)

MariaDB [zxc]>   
MariaDB [zxc]> show tables;    //查看有哪些表
+---------------+
| Tables_in_zxc |
+---------------+
| asd           |
+---------------+
1 row in set (0.000 sec)


//查看当前数据库有哪些表
mysql> SHOW TABLES;
+----------------------+
| Tables_in_wangqingge |
+----------------------+
| wangqing             |
+----------------------+
1 row in set (0.00 sec)


//删除表
//语法：DROP TABLE [ IF EXISTS ] 'table_name';
//删除表asd
MariaDB [zxc]> drop table asd;
Query OK, 0 rows affected (0.001 sec)

MariaDB [zxc]> show tables;
Empty set (0.000 sec)
4.1.3 用户操作

mysql用户帐号由两部分组成，如’USERNAME’@‘HOST’，表示此USERNAME只能从此HOST上远程登录

这里（‘USERNAME’@‘HOST’）的HOST用于限制此用户可通过哪些主机远程连接mysql程序，其值可为：

  • IP地址，如：172.16.12.129
  • 通配符
    • %：匹配任意长度的任意字符，常用于设置允许从任何主机登录
    • _：匹配任意单个字符
//数据库用户创建
//语法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password'];
//创建数据库用户chenshunli
MariaDB [(none)]>  create user 'chenshunli'@'%'  identified by "123"  ;
Query OK, 0 rows affected (0.000 sec)


//使用新创建的用户和密码登录
[root@localhost etc]# mysql -uchenshunli  -p123 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 22
Server version: 10.3.28-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)]> 

//删除数据库用户
//语法：DROP USER 'username'@'host'; 
[root@localhost etc]# mysql -uroot -p123   //退出用户后，切换root用户在进行删除操作
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 23
Server version: 10.3.28-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)]> drop user 'chenshunli'@'%'  ;  
Query OK, 0 rows affected (0.000 sec)
4.1.4 查看命令SHOW
MariaDB [(none)]> SHOW CHARACTER SET;      //查看支持的所有字符集

+----------+-----------------------------+---------------------+--------+
| Charset  | Description                 | Default collation   | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
| dec8     | DEC West European           | dec8_swedish_ci     |      1 |
| cp850    | DOS West European           | cp850_general_ci    |      1 |
| hp8      | HP West European            | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
| swe7     | 7bit Swedish                | swe7_swedish_ci     |      1 |
| ascii    | US ASCII                    | ascii_general_ci    |      1 |
| ujis     | EUC-JP Japanese             | ujis_japanese_ci    |      3 |
| sjis     | Shift-JIS Japanese          | sjis_japanese_ci    |      2 |
| hebrew   | ISO 8859-8 Hebrew           | hebrew_general_ci   |      1 |

......
......



        
MariaDB [(none)]> SHOW ENGINES \G   //查看当前数据库支持的所有存储引擎
*************************** 1. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: MRG_MyISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: CSV
     Support: YES
     Comment: Stores tables as CSV files
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************


 
MariaDB [(none)]> SHOW DATABASES;     //查看数据库信息
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| zxc                |
+--------------------+
4 rows in set (0.000 sec)





MariaDB [(none)]> SHOW TABLES FROM  zxc;      //不进入某数据库而列出其包含的所有表
+---------------+
| Tables_in_zxc |
+---------------+
| asd           |
+---------------+
1 row in set (0.000 sec)


//查看表结构
//语法：DESC [db_name.]table_name;
MariaDB [(none)]> desc zxc.asd ;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| id    | int(7)     | YES  |     | NULL    |       |
| name  | varchar(5) | NO   |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
2 rows in set (0.001 sec)






//查看某表的创建命令
//语法：SHOW CREATE TABLE table_name;
MariaDB [(none)]> show create table zxc.asd;
+-------+----------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                         |
+-------+----------------------------------------------------------------------------------------------------------------------+
| asd   | CREATE TABLE `asd` (
  `id` int(7) DEFAULT NULL,
  `name` varchar(5) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)





//查看某表的状态
//语法：SHOW TABLE STATUS LIKE 'table_name'\G

MariaDB [(none)]> use zxc ;     //进入数据库zxc
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [zxc]> 

MariaDB [zxc]> show table status like 'asd'   \G
*************************** 1. row ***************************
            Name: asd
          Engine: InnoDB
         Version: 10
      Row_format: Dynamic
            Rows: 0
  Avg_row_length: 0
     Data_length: 16384
 Max_data_length: 0
    Index_length: 0
       Data_free: 0
  Auto_increment: NULL
     Create_time: 2021-08-23 21:47:47
     Update_time: NULL
      Check_time: NULL
       Collation: latin1_swedish_ci
        Checksum: NULL
  Create_options: 
         Comment: 
Max_index_length: 0
       Temporary: N
1 row in set (0.000 sec)
4.1.5 获取帮助
//获取命令使用帮助
//语法：HELP keyword;
mysql> HELP CREATE TABLE;       //获取创建表的帮助
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    [IGNORE | REPLACE]
    [AS] query_expression
 ......
 ......
4.1.5 获取帮助
//获取命令使用帮助
//语法：HELP keyword;
mysql> HELP CREATE TABLE;       //获取创建表的帮助
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    [IGNORE | REPLACE]
    [AS] query_expression
 ......
 ......

4.2 DML操作

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

4.2.1 INSERT语句
//DML操作之增操作insert
//语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...

MariaDB [(none)]> use zxc ;

Database changed

MariaDB [zxc]>  insert into asd(id,name)  value(1,'csl') ;       //一次插入一条记录
Query OK, 1 row affected (0.001 sec)


MariaDB [zxc]>  insert into asd(id,name)  values(1,'csl') ,(2,'xk') ,(3,'cac')  ;    //一次插入多条记录
Query OK, 3 rows affected (0.001 sec)  
Records: 3  Duplicates: 0  Warnings: 0
4.2.2 SELECT语句

字段column表示法

表示符代表什么？
*所有字段
as字段别名，如col1 AS alias1 当表名很长时用别名代替

条件判断语句WHERE

操作类型常用操作符
操作符>，<，>=，<=，=，!= BETWEEN column# AND column# LIKE：模糊匹配 RLIKE：基于正则表达式进行模式匹配 IS NOT NULL：非空 IS NULL：空
条件逻辑操作AND OR NOT

ORDER BY：排序，默认为升序（ASC）

ORDER BY语句意义
ORDER BY ‘column_name’根据column_name进行升序排序
ORDER BY ‘column_name’ DESC根据column_name进行降序排序
ORDER BY ’column_name’ LIMIT 2根据column_name进行升序排序 并只取前2个结果
ORDER BY ‘column_name’ LIMIT 1,2根据column_name进行升序排序 并且略过第1个结果取后面的2个结果
//DML操作之查操作select
//语法：SELECT column1,column2,... FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];

MariaDB [(none)]> use zxc ;

Database changed
MariaDB [zxc]> select * from asd ;
+------+------+
| id   | name |
+------+------+
|    1 | csl  |
|    1 | csl  |
|    2 | xk   |
|    3 | cac  |
+------+------+
4 rows in set (0.000 sec)


MariaDB [zxc]> select name from asd;
+------+
| name |
+------+
| csl  |
| csl  |
| xk   |
| cac  |
+------+
4 rows in set (0.000 sec)

MariaDB [zxc]> select  name  from asd   where  id=2 ;
+------+
| name |
+------+
| xk   |
+------+
1 row in set (0.000 sec)


MariaDB [zxc]>  select * from asd  where name='xk' and id=2 ;
+------+------+
| id   | name |
+------+------+
|    2 | xk   |
+------+------+
1 row in set (0.000 sec)



MariaDB [zxc]>  select * from asd order by name ;
+------+------+
| id   | name |
+------+------+
|    3 | cac  |
|    1 | csl  |
|    1 | csl  |
|    2 | xk   |
+------+------+
4 rows in set (0.000 sec)


MariaDB [zxc]>  select * from asd order by name desc ;
+------+------+
| id   | name |
+------+------+
|    2 | xk   |
|    1 | csl  |
|    1 | csl  |
|    3 | cac  |
+------+------+
4 rows in set (0.000 sec)


MariaDB [zxc]>  select * from asd order by name limit 2 ;
+------+------+
| id   | name |
+------+------+
|    3 | cac  |
|    1 | csl  |
+------+------+
2 rows in set (0.000 sec)


MariaDB [zxc]>  select * from asd order by id limit 1,2 ;
+------+------+
| id   | name |
+------+------+
|    1 | csl  |
|    2 | xk   |
+------+------+
2 rows in set (0.000 sec)
# sql
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直接通过javascript-obfuscator命令行混淆js代码

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错误：“Cannot load JDBC driver class 'com.mysql.jdbc.Driver”的解决方法

“Cannot load JDBC driver class 'com.mysql.jdbc.Driver ” 表示没有JDBC连接MySql的驱动包，因此需要手动添加驱动包到WEB-INF目录下的lib目录中。从网上下载驱动包mysql-connector-java-5.1.5.zip，解压缩后将mysql-connector-java-5.1.5-bin.jar放到“**/w...

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