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

MySQL：MySQL（5.7版本最后一版免费，8.0版本收费），MariaDB（10.0版本免费），Percona-Server
PostgreSQL：简称为pgsql
Oracle //收费
MSSQL //隶属于微软

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（很难用到）
• 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（公司用的较多）
• 程序包管理器管理的程序包：
  rpm：有两种
  1、 OS Vendor：操作系统发行商提供的
  2、项目官方提供的
  deb

现在演示在虚拟机上安装mysql 5.7版本如下：
1、去官网http://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm下载rpm包。
2、使用xftp将文件拖入到Xshell，如图所示。

3、去Xshell查看文件。

[root@localhost ~]# ls
anaconda-ks.cfg  mysql80-community-release-el7-3.noarch.rpm

4、安装mysql的安装工具。

[root@localhost ~]# rpm -ivh mysql80-community-release-el7-3.noarch.rpm

5、修改配置文件

[root@localhost ~]# cd /etc/yum.repos.d/
[root@localhost yum.repos.d]# vim mysql-community.repo
# Enable to use MySQL 5.7
[mysql57-community]
name=MySQL 5.7 Community Server
baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
enabled=1  //改为1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql

[mysql80-community]
name=MySQL 8.0 Community Server
baseurl=http://repo.mysql.com/yum/mysql-8.0-community/el/7/$basearch/
enabled=0  //改为0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql

6、安装mysql。

[root@localhost yum.repos.d]# yum module disable mysql
[root@localhost yum.repos.d]# yum -y install mysql-community-server

7、检查是否安装成功。

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

2.2 mysql配置

[root@localhost ~]# grep "password" /var/log/mysqld.log
2021-04-28T15:30:51.475469Z 1 [Note] A temporary password is generated for root@localhost: V*aI4u0hh<e: //此处即为原始密码
2021-04-28T16:01:54.377778Z 2 [Note] Access denied for user 'root'@'localhost' (using password: YES)
2021-04-28T16:03:15.714219Z 3 [Note] Access denied for user 'root'@'localhost' (using password: YES)
[root@localhost ~]# mysql -uroot -p
Enter password:      //手动输入或者复制粘贴V*aI4u0hh<e:即可
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 4
Server version: 5.7.34

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

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

mysql>   //看到有这样的标识表示登录成功了

//修改mysql登录密码
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'lixirong123!';  //设置密码
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye
//成功设置

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：备份工具
• 服务器端
  mysqld

执行安全初始化

[root@localhost ~]# mysql_secure_installation

Securing the MySQL server deployment.

Enter password for user root:   //使用修改过的密码登录（默认可以回车）
The 'validate_password' plugin is installed on the server.
The subsequent steps will run with the existing configuration
of the plugin.
Using existing password for root.

Estimated strength of the password: 50 
Change the password for root ? ((Press y|Y for Yes, any other key for No) : n  //是否修改root账户密码

 ... skipping.
By default, a MySQL installation has an anonymous user,
allowing anyone to log into MySQL 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? (Press y|Y for Yes, any other key for No) : 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? (Press y|Y for Yes, any other key for No) : n  //要不要拒绝root账户远程登录

 ... skipping.
By default, MySQL 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? (Press y|Y for Yes, any other key for No) : Y  //删除测试数据库并访问它的权限
 - 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? (Press y|Y for Yes, any other key for No) : Y  //重新加载权限表
Success.

All done! 

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
    

3.2 服务器监听的两种socket地址

4. mysql数据库操作

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

//创建数据库
//语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME'; //中括号中的内容可有可无，它的区别在于判断你曾经是否创建过，可执行多遍，不会报错，假如不带中括号的内容如果之前创建了就会报错。

//查看当前实例有哪些数据库，执行SHOW DATABASES;的时候是不区分大小写的，一般还是写成大写，能够看得更清楚，能够区分，注意一定要带分号；。
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> 

//创建一个school应用实例
mysql> CREATE DATABASE school;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> 

删除数据库

//删除数据库
//语法：DROP DATABASE [IF EXISTS] 'DB_NAME';  //解释同创建数据库

//应用实例，删除school数据库
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> DROP DATABASE IF EXISTS school;
Query OK, 0 rows affected (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

4.1.2 表操作

```bash
//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';
```mysql> CREATE DATABASE hehe;
Query OK, 1 row affected (0.00 sec)

//应用实例，创建一个数据库呵呵和一个表格wodebiaoge
mysql> use hehe;
Database changed
mysql> SHOW TABLES;
Empty set (0.00 sec)

mysql> CREATE TABLE wodebiaoge(id int not null,name varchar(100) null,age tinyint);
Query OK, 0 rows affected (0.02 sec)

mysql> SHOW TABLES;
+----------------+
| Tables_in_hehe |
+----------------+
| wodebiaoge     |
+----------------+
1 row in set (0.01 sec)

mysql> 

//删除表格
//删除表
//语法：DROP TABLE [ IF EXISTS ] 'table_name';

//应用实例，删除wodebiaoge
mysql> DROP TABLE wodebiaoge;
Query OK, 0 rows affected (0.01 sec)

mysql> SHOW TABLES;
Empty set (0.00 sec)
mysql> 

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（例如tom@172.16.12.129，表示tom只能从这个IP连接主机数据库）
• 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（例如tom@%，表示tom可以从任何主机登录）
  _：匹配任意单个字符

//数据库用户创建
//语法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password'];
//删除数据库用户
//语法：DROP USER 'username'@'host'; 

4.1.4 查看命令SHOW

mysql> 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 |
| tis620   | TIS620 Thai                     | tis620_thai_ci      |      1 |
| euckr    | EUC-KR Korean                   | euckr_korean_ci     |      2 |
| koi8u    | KOI8-U Ukrainian                | koi8u_general_ci    |      1 |
| gb2312   | GB2312 Simplified Chinese       | gb2312_chinese_ci   |      2 |
| greek    | ISO 8859-7 Greek                | greek_general_ci    |      1 |
| cp1250   | Windows Central European        | cp1250_general_ci   |      1 |
| gbk      | GBK Simplified Chinese          | gbk_chinese_ci      |      2 |
| latin5   | ISO 8859-9 Turkish              | latin5_turkish_ci   |      1 |
| armscii8 | ARMSCII-8 Armenian              | armscii8_general_ci |      1 |
| utf8     | UTF-8 Unicode                   | utf8_general_ci     |      3 |
| ucs2     | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
| cp866    | DOS Russian                     | cp866_general_ci    |      1 |
| keybcs2  | DOS Kamenicky Czech-Slovak      | keybcs2_general_ci  |      1 |
| macce    | Mac Central European            | macce_general_ci    |      1 |
| macroman | Mac West European               | macroman_general_ci |      1 |
| cp852    | DOS Central European            | cp852_general_ci    |      1 |
| latin7   | ISO 8859-13 Baltic              | latin7_general_ci   |      1 |
| utf8mb4  | UTF-8 Unicode                   | utf8mb4_general_ci  |      4 |
| cp1251   | Windows Cyrillic                | cp1251_general_ci   |      1 |
| utf16    | UTF-16 Unicode                  | utf16_general_ci    |      4 |
| utf16le  | UTF-16LE Unicode                | utf16le_general_ci  |      4 |
| cp1256   | Windows Arabic                  | cp1256_general_ci   |      1 |
| cp1257   | Windows Baltic                  | cp1257_general_ci   |      1 |
| utf32    | UTF-32 Unicode                  | utf32_general_ci    |      4 |
| binary   | Binary pseudo charset           | binary              |      1 |
| geostd8  | GEOSTD8 Georgian                | geostd8_general_ci  |      1 |
| cp932    | SJIS for Windows Japanese       | cp932_japanese_ci   |      2 |
| eucjpms  | UJIS for Windows Japanese       | eucjpms_japanese_ci |      3 |
| gb18030  | China National Standard GB18030 | gb18030_chinese_ci  |      4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)

mysql> show engines;  //查看当前数据库支持的所有存储引擎
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)

mysql> show databases;  //查看数据库信息
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hehe               |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.06 sec)

mysql> show tables from mysql;  //不进入某数据库列出其所包含的表
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| engine_cost               |
| event                     |
| func                      |
| general_log               |
| gtid_executed             |
| help_category             |
| help_keyword              |
| help_relation             |
| help_topic                |
| innodb_index_stats        |
| innodb_table_stats        |
| ndb_binlog_index          |
| plugin                    |
| proc                      |
| procs_priv                |
| proxies_priv              |
| server_cost               |
| servers                   |
| slave_master_info         |
| slave_relay_log_info      |
| slave_worker_info         |
| slow_log                  |
| tables_priv               |
| time_zone                 |
| time_zone_leap_second     |
| time_zone_name            |
| time_zone_transition      |
| time_zone_transition_type |
| user                      |
+---------------------------+
31 rows in set (0.00 sec)

//查看表结构
//语法：DESC [db_name.]table_name;
mysql> desc mysql.user;  //查看mysql数据库下面的user表

//查看某表的创建命令
//语法：SHOW CREATE TABLE table_name;
mysql> SHOW CREATE TABLE mysql.user;  //查看user表的创建命令

//查看某表的状态
//语法：SHOW TABLE STATUS LIKE 'table_name'G
mysql> use mysql;
mysql> SHOW TABLE STATUS LIKE 'user'G; //查看user表的状态

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,...),(...),...
mysql> insert class1 (id,name,age) value (1,'tom',20);  //一次插入一条记录
Query OK, 1 row affected (0.01 sec)

mysql> select * from class1;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
+----+------+------+
1 row in set (0.00 sec)
mysql> insert class1 (id,name,age) VALUES (2,'jerry',23),(3,'wangqing'',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',NUULL);   //一次插入多张表，将value改成values
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> select * from class1;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | wangqing  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

4.2.2 SELECT语句

字段column表示法

条件判断语句WHERE

ORDER BY：排序，默认为升序（ASC）

//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];
```mysql> select * from class1;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | wangqing  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT name FROM class1;     //根据名字显示
+-----------+
| name      |
+-----------+
| tom       |
| jerry     |
| wangqing  |
| sean      |
| zhangshan |
| zhangshan |
| lisi      |
+-----------+


7 rows in set (0.00 sec)
mysql> select * from class1 order by age;    //根据年龄进行升序排序
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      | NULL |
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
|  2 | jerry     |   23 |
|  3 | wangqing  |   25 |
|  5 | zhangshan |   26 |
|  4 | sean      |   28 |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> select * from class1 order by age desc;   //根据年龄进行降序排序
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  3 | wangqing  |   25 |
|  2 | jerry     |   23 |
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)


mysql> select * from class1 order by age limit 1,2;   //根据年龄升序排序并且略过第1个结果取后面的2个结果
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
+----+-----------+------+
2 rows in set (0.00 sec)


mysql> select * from class1 order by age limit 2;  //根据年龄进行升序排序
并只取前2个结果
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
|  1 | tom  |   20 |
+----+------+------+
2 rows in set (0.00 sec)


mysql> select * from class1 where age >=25 and name = 'zhangshan';  //年龄大于等于25岁的名字
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | zhangshan |   26 |
+----+-----------+------+
1 row in set (0.00 sec)

4.2.3 update语句

/DML操作之改操作update
//语法：UPDATE table_name SET column1 = new_value1[,column2 = new_value2,...] [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
mysql> update class1 set age = 30 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from class1 where name = 'lisi';
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi |   30 |
+----+------+------+
1 row in set (0.00 sec)

4.2.4 delete语句

//DML操作之删操作delete
//语法：DELETE FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];

mysql> delete from class1;
Query OK, 7 rows affected (0.00 sec)

mysql> select * from class1; //删除整张表
Empty set (0.00 sec)

mysql> desc class1;
+-------+-------------+------+-----+---------+-------+
| 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 (0.01 sec)

4.2.5 truncate语句

truncate与delete的区别：

/语法：TRUNCATE table_name;
mysql> select * from class1;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | wangqing  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> truncate class1;
Query OK, 0 rows affected (0.01 sec)

mysql> select * from class1;
Empty set (0.00 sec)

mysql> desc class1;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.3 DCL操作

4.3.1 创建授权grant

权限类型(priv_type)

指定要操作的对象db_name.table_name

WITH GRANT OPTION：被授权的用户可将自己的权限副本转赠给其他用户，说白点就是将自己的权限完全复制给另一个用户。不建议使用。

mysql> show databases;+--------------------+
| Database           |
+--------------------+
| information_schema |
| hehe               |
| lixirong           |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+
7 rows in set (0.00 sec)

//授权lixirong用户在数据库本机上登录访问所有数据库
mysql> GRANT ALL ON *.* TO 'lixirong'@'localhost' IDENTIFIED BY 'lixirong123!';

//授权lixirong用户在192.168.249.140上远程登录访问lixirong数据库
mysql> GRANT ALL ON lixirong.* TO 'lixirong'@'192.168.249.140' IDENTIFIED BY 'lixirong123!';

//授权lixirong用户在所有位置上远程登录访问lixirong数据库
mysql> GRANT ALL ON *.* TO 'lixirong'@'%' IDENTIFIED BY 'lixirong123!';

4.3.2 查看授权

//查看当前用户的授权信息
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)

4.3.3 取消授权REVOKE

//语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';

注意：mysql服务进程启动时会读取mysql库中的所有授权表至内存中：

• GRANT或REVOKE等执行权限操作会保存于表中，mysql的服务进程会自动重读授权表，并更新至内存中
• 对于不能够或不能及时重读授权表的命令，可手动让mysql的服务进程重读授权表

mysql> FLUSH PRIVILEGES;

最后

以上就是时尚蜡烛为你收集整理的MySQL基础操作1. 关系型数据库介绍2.mysql安装与配置3. mysql的程序组成4. mysql数据库操作的全部内容，希望文章能够帮你解决MySQL基础操作1. 关系型数据库介绍2.mysql安装与配置3. mysql的程序组成4. mysql数据库操作所遇到的程序开发问题。

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