Liunx服务管理之mysql基础

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
DDL CREATE:创建
DROP:删除
ALTER:修改
DML INSERT: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
DCL xGRANT: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
#配置mysql的yum源
wget -O /usr/src/mysql57-community-release-el7-10.noarch.rpm \
http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
rpm -Uvh /usr/src/mysql57-community-release-el7-10.noarch.rpm

#安装mysql5.7
yum -y install mysql-community-server mysql-community-client  \
mysql-community-common mysql-community-devel

2.2 mysql配置

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

#确保3306端口已经监听起来
ss -antl

#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@longnian ~]# mysql -uroot -p
Enter password:     //此处输入密码,可以直接复制你的密码粘贴至此处,也可手动输入
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.23

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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>          //看到有这样的标识符则表示成功登录了





//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 (0.01 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye



//为避免mysql自动升级,这里需要卸载最开始安装的yum源
rpm -e mysql57-community-release

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@longnian ~]# mysql -V
mysql  Ver 14.14 Distrib 5.7.23, for Linux (x86_64) using  EditLine wrapper



[root@longnian ~]# mysql -uroot -plongnian@123 -h192.168.159.135
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> 

//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 ~]# mysql -uroot -p -h192.168.159.135
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> 


[root@localhost ~]# mysql -uroot -p -h 192.168.159.135 -e 'SHOW DATABASES;'
Enter password:
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| student         |
+--------------------+

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student
mysql> CREATE DATABASE IF NOT EXISTS student;
Query OK, 1 row affected (0.00 sec)

//查看当前实例有哪些数据库
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| student         |
+--------------------+
5 rows in set (0.00 sec)

//删除数据库
//语法:DROP DATABASE [IF EXISTS] 'DB_NAME';
//删除数据库student
mysql> DROP DATABASE IF EXISTS student;
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

//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wangqingge里创建表longnian
mysql> CREATE DATABASE student;      //创建数据库student
Query OK, 1 row affected (0.00 sec)

mysql> use student;      //进入student数据库
Database changed
mysql> CREATE TABLE longnian (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint);      //创建longnian表
Query OK, 0 rows affected (0.09 sec)


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


//删除表
//语法:DROP TABLE [ IF EXISTS ] 'table_name';
//删除表longnian
mysql> DROP TABLE longnian;
Query OK, 0 rows affected (0.01 sec)

mysql> SHOW TABLES;
Empty set (0.00 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longnian
mysql> CREATE USER 'longnian'@'192.168.159.135' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected (0.00 sec)

//使用新创建的用户和密码登录
[root@localhost ~]# mysql -ulongnian -plongnian@123 -h192.168.159.135
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> 

//删除数据库用户
//语法:DROP USER 'username'@'host'; 
mysql> DROP USER 'longnian'@'192.168.159.135';
Query OK, 0 rows affected (0.00 sec)

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 | 
......
......



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 |
| mysql              |
| performance_schema |
| sys                |
| longnian         |
+--------------------+
5 rows in set (0.00 sec)



mysql> SHOW TABLES FROM student;         //不进入某数据库而列出其包含的所有表
+----------------------+
| Tables_in_student |
+----------------------+
| longnian             |
+----------------------+
1 row in set (0.00 sec)



//查看表结构
//语法:DESC [db_name.]table_name;
mysql> DESC student.longnian;
+-------+--------------+------+-----+---------+-------+
| 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 (0.03 sec)





//查看某表的创建命令
//语法:SHOW CREATE TABLE table_name;
mysql> SHOW CREATE TABLEstudent.longnian;
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                              |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| wangqing | CREATE TABLE `longnian` (
  `id` int(11) NOT NULL,
  `name` varchar(100) NOT NULL,
  `age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)





//查看某表的状态
//语法:SHOW TABLE STATUS LIKE 'table_name'\G
mysql> use student;      //进入数据库student
Database changed
mysql> SHOW TABLE STATUS LIKE 'longnian'\G      //查看longnian表的状态
*************************** 1. row ***************************
           Name: longnian
         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: 2020-05-20 16:19:35
    Update_time: NULL
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.00 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
 ......
 ......

4.2 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> use student;
Database changed
mysql> INSERT INTO longnian (id,name,age) VALUE (1,'tom',20);       //一次插入一条记录
Query OK, 1 row affected (0.01 sec)


mysql> INSERT INTO longnian (id,name,age) VALUES (2,'jerry',23),(3,'longnian',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',NULL);     //一次插入多条记录
Query OK, 4 rows affected (0.01 sec)
Records: 4  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
vRLIKE: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];

mysql> use student;
Database changed
mysql> select * from longnian;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  6 | xiaowang |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT name FROM longnian;
+-----------+
| name      |
+-----------+
| tom       |
| jerry     |
| xiaoming  |
| xiaoai      |
| xiaoli |
| xiaowang |
| lisi      |
+-----------+
7 rows in set (0.01 sec)

mysql> SELECT * FROM longnian ORDER BY age;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      | NULL |
|  1 | tom       |   20 |
|  6 | xiaowang |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  5 | xiaoli |   26 |
|  4 | xiaoai      |   28 |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT * FROM longnian ORDER BY age DESC;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  3 | xiaoming  |   25 |
|  2 | jerry     |   23 |
|  1 | tom       |   20 |
|  6 | xiaowang |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT * FROM longnian ORDER BY age limit 2;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
|  1 | tom  |   20 |
+----+------+------+
2 rows in set (0.00 sec)

mysql> SELECT * FROM longnian ORDER BY age limit 1,2;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  6 | xiaowang |   20 |
+----+-----------+------+
2 rows in set (0.00 sec)


mysql> SELECT * FROM longnian WHERE age >= 25;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
+----+-----------+------+
3 rows in set (0.00 sec)

mysql> SELECT * FROM longnian WHERE age >= 25 AND name = 'zhangshan';
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | xiaoli |   26 |
+----+-----------+------+
1 row in set (0.00 sec)

mysql> SELECT * FROM longnian WHERE age BETWEEN 23 and 28;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
+----+-----------+------+
4 rows in set (0.00 sec)

mysql> select * from longnian where age is not null;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  6 | xiaowang |   20 |
+----+-----------+------+
6 rows in set (0.00 sec)

mysql> select * from longnian where age is null;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
+----+------+------+
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> select * from longnian;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  6 | xiaowang |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> update longnian set age = 30 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

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

mysql> delete from longnian where id = 7;       //删除某条记录
Query OK, 1 row affected (0.00 sec)

mysql> select * from wangqing;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  6 | xiaowang |   20 |
+----+-----------+------+
6 rows in set (0.00 sec)


mysql> delete from longnian;        //删除整张表的内容
Query OK, 6 rows affected (0.00 sec)

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

mysql> desc longnian;
+-------+--------------+------+-----+---------+-------+
| 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)

4.2.5 truncate语句

truncate与delete的区别:

语句类型 特点
delete DELETE删除表内容时仅删除内容,但会保留表结构
DELETE语句每次删除一行,并在事务日志中为所删除的每行记录一项
可以通过回滚事务日志恢复数据
非常占用空间
truncate 删除表中所有数据,且无法恢复
表结构、约束和索引等保持不变,新添加的行计数值重置为初始值
执行速度比DELETE快,且使用的系统和事务日志资源少
通过释放存储表数据所用的数据页来删除数据,并且只在事务日志中记录页的释放
对于有外键约束引用的表,不能使用TRUNCATE TABLE删除数据
不能用于加入了索引视图的表
//语法:TRUNCATE table_name;

mysql> select * from longnian;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xiaoming  |   25 |
|  4 | xiaoai      |   28 |
|  5 | xiaoli |   26 |
|  6 | xiaowang |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

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

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

mysql> desc longnian;
+-------+--------------+------+-----+---------+-------+
| 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)

权限类型 代表什么?
ALL 所有权限
SELECT 读取内容的权限
INSERT 插入内容的权限
UPDATE 更新内容的权限
DELETE 删除内容的权限

指定要操作的对象db_name.table_name

表示方式 意义
* . * 所有库的所有表
db_name 指定库的所有表
db_name.table_name 指定库的指定表

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。

GRANT priv_type,... ON [object_type] db_name.table_name TO ‘username'@'host' [IDENTIFIED BY 'password'] [WITH GRANT OPTION];

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

//授权wangqing用户在数据库本机上登录访问所有数据库
mysql> GRANT ALL ON *.* TO 'longnian'@'localhost' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> GRANT ALL ON *.* TO 'longnian'@'192.168.159.135' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected, 1 warning (0.00 sec)

//授权longnian用户在192.168.159.132上远程登录访问student数据库
mysql> GRANT ALL ON student.* TO 'wangqing'@'192.168.159.135' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected, 1 warning (0.00 sec)

//授权longnian用户在所有位置上远程登录访问student数据库
mysql> GRANT ALL ON *.* TO 'longnian'@'%' IDENTIFIED BY 'longnian@123';
Query OK, 0 rows affected, 1 warning (0.00 sec)

4.3.2 查看授权

//查看当前登录用户的授权信息
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)

//查看指定用户longnian的授权信息
mysql> SHOW GRANTS FOR longnian;
+-----------------------------------------------+
| Grants for longnian@%                         |
+-----------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'longnian'@'%' |
+-----------------------------------------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'longnian'@'localhost';
+-------------------------------------------------------+
| Grants for longnian@localhost                         |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'longnian'@'localhost' |
+-------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'longnian'@'192.168.159.135';
+-------------------------------------------------------+
| Grants for [email protected]                         |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'longnian'@'192.168.159.135' |
+-------------------------------------------------------+
1 row 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';

mysql> REVOKE ALL ON *.* FROM 'longnian'@'192.168.159.132';
Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

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;

5.4实例

1.搭建mysql服务

[root@longnian ~]# systemctl stop firewalld.service  关闭防火墙
[root@longnian ~]# setenforce 0  关闭setLinux服务
[root@longnian ~]# cd /usr/src
[root@longnian src]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
[root@longnian src]# rpm -ivh mysql57-community-release-el7-10.noarch.rpm
[root@longnian src]# cd /etc/yum.repos.d      
[root@longnian yum.repos.d]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel
[root@longnian yum.repos.d]# systemctl start mysqld 启动mysqld服务
[root@longnian yum.repos.d]# systemctl status mysqld
[root@longnian yum.repos.d]# systemctl enable mysqld 开机启动
[root@longnian ~]# grep "password" /var/log/mysqld.log
2020-05-22T14:01:03.148212Z 1 [Note] A temporary password is generated for root@localhost: 1.*%ZQzys#/j
[root@longnian ~]# mysql -uroot -p1.*%ZQzys#/j
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.30

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

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> 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 'longnian@123!';
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

2.创建一个以你名字为名的数据库,并创建一张表student,该表包含三个字段(id,name,age),表结构如下:

mysql> desc student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| name  | varchar(100) | NO   |     | NULL    |                |
| age   | tinyint(4)   | YES  |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
mysql> create database longnian;
Query OK, 1 row affected (0.00 sec)

mysql> use longnian
Database changed
mysql> create table student(id int(11) NOT NULL Key auto_increment,name CHAR(100) NOT NULL,age tinyint NULL);
Query OK, 0 rows affected (0.00 sec)

mysql> DESC longnian.student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| name  | varchar(100) | NO   |     | NULL    |                |
| age   | tinyint(4)   | YES  |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)

3.查看下该新建的表有无内容(用select语句)

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

4.往新建的student表中插入数据(用insert语句),结果应如下所示:

+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
mysql> insert into student (id,name,age)values (1,'tom',20),(2,'jerry',23),(3,'wangqing',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',NULL),(8,'chenshuo',10),(9,'wangwu',3),(10,'qiuyi',15),(11,'qiuxiaotian',20););
mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)

5.修改lisi的年龄为50

mysql> update student set age = 50 where name = 'lisi';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)

6.以age字段降序排序

mysql> select * from student order by age desc;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  7 | lisi        |   50 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  3 | wangqing    |   25 |
|  2 | jerry       |   23 |
|  1 | tom         |   20 |
|  6 | zhangshan   |   20 |
| 11 | qiuxiaotian |   20 |
| 10 | qiuyi       |   15 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
+----+-------------+------+
11 rows in set (0.00 sec)

7.查询student表中年龄最小的3位同学跳过前2位

mysql> select * from student order by age limit 2,3;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  6 | zhangshan   |   20 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+----------+------+
3 rows in set (0.00 sec)

8.查询student表中年龄最大的4位同学

mysql> select * from student order by age desc limit 4;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      |   50 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  3 | wangqing  |   25 |
+----+-----------+------+
4 rows in set (0.00 sec)

9.查询student表中名字叫zhangshan的记录

mysql> select name from student where name='zhangshan';
+-----------+
| name      |
+-----------+
| zhangshan |
| zhangshan |
+-----------+
2 rows in set (0.00 sec)

10.查询student表中名字叫zhangshan且年龄大于20岁的记录

mysql> select name from student where age>20 and name='zhangshan';
+-----------+
| name      |
+-----------+
| zhangshan |
+-----------+
1 row in set (0.00 sec)

11.查询student表中年龄在23到30之间的记录

mysql> select name from student where age between 23 and 30 ;
+-----------+
| name      |
+-----------+
| jerry     |
| wangqing  |
| sean      |
| zhangshan |
+-----------+
4 rows in set (0.00 sec)

12.修改wangwu的年龄为100

mysql> update student set age = 100 where name = 'wangwu';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)

13.删除student中名字叫zhangshan且年龄小于等于20的记录

mysql> delete from student where name='zhangshan' and  age <= 20;
Query OK, 1 row affected (0.00 sec)

mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
10 rows in set (0.00 sec)

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