mysql基础

1. 关系型数据库介绍
2. mysql安装与配置
- 2.1 mysql安装
- 2.2 mysql基本配置
3. mysql的程序组成
- 3.1 mysql工具使用
- 3.2 服务器监听的两种socket地址
4. mysql数据库操作

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

关系模型又分为:

二维关系：row(行)，column（列）
数据库管理系统：DBMS（database manager system）
关系数据库管理系统（Relational database manager system）

1.2 RDBMS专业名词

常见的关系型数据库管理系统：

MySQL：MySQL，MariaDB（和MySQL是同源，RHEL7上yum源自带），Percona-Server
PostgreSQL：简称为pgsql
Oracle
MSSQL

事务:多个操作被当作一个整体对待就称为一个事务(整个事务中的所有操作，要么全部完成，要么全部不完成，不可能停滞在中间某个环节。事务在执行过程中发生错误，会被回滚（Rollback）到事务开始前的状态，就像这个事务从来没有执行过一样。)

要看一个关系型数据库是否支持事务，需要看其是否支持并满足ACID测试

ACID:ACID是事务的一个基本标准

A：Automicity，原子性
C：Consistency，一致性
I：Isolation，隔离性
D：Durability，持久性

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

关系运算：

选择：挑选出符合条件的行（部分行）
投影：挑选出需要的字段（一般是列）
连接（将两个表相关联）

数据抽象方式：

物理层：决定数据的存储格式，即RDBMS在磁盘上如何组织文件
逻辑层：描述DB存储什么数据，以及数据间存在什么样的关系
视图层：描述DB中的部分数据

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	GRANT：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：

1.rpm(有两种，os Vendor，项目官方提供)

2.deb

//第一步下载mysql5.7的yum源

[root@cwh ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm

--2019-04-22 15:04:39--  http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm

...

...

2019-04-22 15:04:46 (389 KB/s) - 已保存 “mysql57-community-release-el7-10.noarch.rpm” [25548/25548])

[root@cwh ~]# ls

aaa  anaconda-ks.cfg  cwh4http.sh  httpd.conf  httpd-vhosts.conf  httppz1.sh  mysql57-community-release-el7-10.noarch.rpm

//第二步安装下载下来的mysql源

[root@cwh ~]# yum -y install mysql57-community-release-el7-10.noarch.rpm

[root@cwh ~]# ls /etc/yum.repos.d/

7CentOS-Base.repo  mysql-community.repo  mysql-community-source.repo  redhat.repo

//第三步安装mysql5.7

yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel

2.2 mysql基本配置

//第一步启动mysql并查看端口是否开启

[root@cwh ~]# systemctl start mysqld

[root@cwh ~]# ss -antl

State       Recv-Q Send-Q                     Local Address:Port                                    Peer Address:Port

LISTEN      0      128                                    *:22                                                 *:*

LISTEN      0      100                            127.0.0.1:25                                                 *:*

LISTEN      0      80                                    :::3306                                              :::*

LISTEN      0      128                                   :::22                                                :::*

LISTEN      0      100                                  ::1:25                                                :::*                  

//第二步在mysql日志文件中找出mysql临时密码

[root@cwh ~]# cat /var/log/mysqld.log |grep password

2019-04-22T07:40:39.531315Z 1 [Note] A temporary password is generated for root@localhost: xB>aDF_l>4>;

//最后的xB>aDF_l>4>;为临时密码以后登陆时需要

//第三步使用获取到的临时密码登录mysql

[root@localhost ~]# mysql -uroot -p

Enter password:

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 2

Server version: 5.7.25

Copyright (c) 2000, 2019, 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>   //这样显示出来了就表示临时登录成功

//第四步修改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 'cwh123!';

Query OK, 0 rows affected (0.00 sec)

mysql> quit

Bye

//第五步为避免mysql自动升级，这里需要卸载最开始安装的yum源

[root@localhost ~]# rpm -qa |grep mysql

mysql-community-common-5.7.25-1.el7.x86_64

mysql-community-libs-5.7.25-1.el7.x86_64

mysql-community-libs-compat-5.7.25-1.el7.x86_64

mysql-community-server-5.7.25-1.el7.x86_64

mysql57-community-release-el7-10.noarch

mysql-community-client-5.7.25-1.el7.x86_64

mysql-community-devel-5.7.25-1.el7.x86_64

[root@localhost ~]# yum -y remove mysql57-community-release-el7-10.noarch

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

//查看当前使用的mysql脚本

[root@localhost ~]# mysql -V

mysql  Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using  EditLine wrapper

//本地登录

[root@cwh ~]# mysql -uroot -pcwh123! -h127.0.0.1

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 13

Server version: 5.7.25 MySQL Community Server (GPL)

Copyright (c) 2000, 2019, 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>  //此时显示已经登陆上了

//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@cwh ~]# mysql -uroot -p -h127.0.0.1

Enter password:

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 14

Server version: 5.7.25 MySQL Community Server (GPL)

Copyright (c) 2000, 2019, 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> 

//查看mysql中有哪些数据库

[root@localhost ~]# mysql -uroot -p -h127.0.0.1 -e 'show databases'

Enter password:

+--------------------+

| Database           |

+--------------------+

| information_schema |

| mysql              |

| performance_schema |

| sys                |

+--------------------+

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chengweihong

[root@localhost ~]# mysql -uroot -p

Enter password:

mysql>

mysql> create database if not exists chengweihong;

Query OK, 1 row affected (0.00 sec)

mysql> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| chengweihong       |

| mysql              |

| performance_schema |

| sys                |

+--------------------+

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chengweihong

mysql> drop database if exists chengweihong;

Query OK, 0 rows affected (0.02 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chengweihong里创建表cwh

//首先创建chengweihong数据库

mysql> create database chengweihong;

Query OK, 1 row affected (0.01 sec)

//在在数据库chengweihong中创建表

mysql> create table cwh(id int not null,name varchar(100),age tinyint);

Query OK, 0 rows affected (0.04 sec)

mysql> show tables;

+------------------------+

| Tables_in_chengweihong |

+------------------------+

| cwh                    |

+------------------------+

1 row in set (0.00 sec)

//具体查看表的内容

mysql> desc cwh;

+-------+--------------+------+-----+---------+-------+

| Field | Type         | Null | Key | Default | Extra |

+-------+--------------+------+-----+---------+-------+

| id    | int(11)      | NO   |     | NULL    |       |

| name  | varchar(100) | YES  |     | NULL    |       |

| age   | tinyint(4)   | YES  |     | NULL    |       |

+-------+--------------+------+-----+---------+-------+

3 rows in set (0.03 sec)

//删除表

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

//删除表cwh

mysql> drop table if exists cwh;

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wangqing

mysql> create user cwh@192.168.112.149 identified by 'cwh123!';

Query OK, 0 rows affected (0.01 sec)

//在192.168.112.149上验证

[root@149 ~]# mysql -ucwh -p -h192.168.112.146

Enter password:

Welcome to the MariaDB monitor.  Commands end with ; or \g.

Your MySQL connection id is 19

Server version: 5.7.25 MySQL Community Server (GPL)

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

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

MySQL [(none)]>  //因为没有配置权限所以查看的东西有限，看不到chengweihong的数据库

MySQL [(none)]> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

+--------------------+

1 row in set (0.01 sec)

//删除数据库用户

//语法：DROP USER 'username'@'host';

mysql> drop user cwh@192.168.112.149;

Query OK, 0 rows affected (0.01 sec)

//删除用户后在192.168.112.149主机上验证

[root@149 ~]# mysql -ucwh -p -h192.168.112.146

Enter password:

ERROR 1130 (HY000): Host '192.168.112.149' is not allowed to connect to this MySQL server

//可以看出已经无法登陆了

4.1.4 查看命令SHOW

//1.查看有哪些数据库

mysql> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| chengweihong       |

| mysql              |

| performance_schema |

| sys                |

+--------------------+

5 rows in set (0.00 sec)

//2.查看数据库中有哪些表格（要看那个数据的表格就先进入到数据库中）

mysql> use chengweihong

Database changed

mysql> show tables;

+------------------------+

| Tables_in_chengweihong |

+------------------------+

| cwh                    |

+------------------------+

1 row in set (0.00 sec)

//3.查看支持的所有字符集

mysql> show character set;

+----------+---------------------------------+---------------------+--------+

| 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 (0.01 sec)

//4.查看当前数据库支持的所有存储引擎

mysql> show engines;

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| 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)

//5.不进入某数据库而列出其包含的所有表

mysql> show tables from chengweihong;

+------------------------+

| Tables_in_chengweihong |

+------------------------+

| cwh                    |

+------------------------+

1 row in set (0.00 sec)

//6.查看表结构

//语法：DESC [db_name.]table_name;

mysql> desc chengweihong.cwh;

+-------+--------------+------+-----+---------+-------+

| Field | Type         | Null | Key | Default | Extra |

+-------+--------------+------+-----+---------+-------+

| id    | int(11)      | NO   |     | NULL    |       |

| name  | varchar(100) | YES  |     | NULL    |       |

| age   | tinyint(4)   | YES  |     | NULL    |       |

+-------+--------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

//7.查看某表的创建命令

//语法：SHOW CREATE TABLE table_name;

mysql> show create table cwh;

+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------+

| Table | Create Table                                                                                                                                             |

+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------+

| cwh   | CREATE TABLE `cwh` (

  `id` int(11) NOT NULL,

  `name` varchar(100) DEFAULT 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> show create table cwh\G;

*************************** 1. row ***************************

       Table: cwh

Create Table: CREATE TABLE `cwh` (

  `id` int(11) NOT NULL,

  `name` varchar(100) DEFAULT NULL,

  `age` tinyint(4) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=latin1

1 row in set (0.00 sec)

4.1.5 获取帮助

//获取创建表的帮助

mysql> help create table

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

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name

    { LIKE old_tbl_name | (LIKE old_tbl_name) }

4.2 DML操作（数据操控语言）

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

1.一次插入一条完整数据

mysql> insert into cwh value(1,'tom',10);

Query OK, 1 row affected (0.01 sec)

mysql> select * from cwh;

+----+------+------+

| id | name | age  |

+----+------+------+

|  1 | tom  |   10 |

+----+------+------+

1 row in set (0.00 sec)

2.一次插入多条完整数据

mysql> insert into cwh values(2,'jerry',20),(3,'natasha',30)

    -> ; //因为最后没有输入分号

Query OK, 2 rows affected (0.01 sec)

Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from cwh

    -> ;  //因为ui后没输入；

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

+----+---------+------+

3 rows in set (0.00 sec)

3.一次插入一条指定字段的数据

mysql> insert into cwh(id,name) value(4,'aaa');

Query OK, 1 row affected (0.00 sec)

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     | NULL |

+----+---------+------+

4 rows in set (0.00 sec)

4.一次插入多条指定字段的数据

mysql> insert into cwh(id,name) values(5,'bbb'),(6,'ccc');

Query OK, 2 rows affected (0.00 sec)

Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from cwh

    -> ;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     | NULL |

|  5 | bbb     | NULL |

|  6 | ccc     | NULL |

+----+---------+------+

6 rows in set (0.00 sec)

4.2.2 SELECT语句

字段column表示法

表示符	表示
*	所有字段
as	字段别名, 当名字很长时用别名代替

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];

1.查看表的所有内容

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     | NULL |

|  5 | bbb     | NULL |

|  6 | ccc     | NULL |

+----+---------+------+

6 rows in set (0.00 sec)

2.按字段查看表的内容

mysql> select name from cwh;

+---------+

| name    |

+---------+

| tom     |

| jerry   |

| natasha |

| aaa     |

| bbb     |

| ccc     |

+---------+

6 rows in set (0.00 sec)

3.查看表的内容并按某字段升序排序

mysql> select * from cwh order by age;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  4 | aaa     | NULL |

|  5 | bbb     | NULL |

|  6 | ccc     | NULL |

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

+----+---------+------+

6 rows in set (0.00 sec)

4.查看表的内容按升序排序取前两个

mysql> select * from cwh order by id limit 2;

+----+-------+------+

| id | name  | age  |

+----+-------+------+

|  1 | tom   |   10 |

|  2 | jerry |   20 |

+----+-------+------+

2 rows in set (0.00 sec)

5.查看表的内容按升序排序跳过第一个取后两个

mysql> select * from cwh order by id limit 1,2;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

+----+---------+------+

2 rows in set (0.00 sec)

6.查看表的内容只打印age大于25的信息

mysql> select * from cwh where age >=25;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  3 | natasha |   30 |

+----+---------+------+

1 row in set (0.00 sec)

7.查看表的内容只打印age=25和name=tom的信息

mysql> select * from cwh where age=10 and name='tom';

+----+------+------+

| id | name | age  |

+----+------+------+

|  1 | tom  |   10 |

+----+------+------+

1 row in set (0.00 sec)

8.查看表格打印id在2-4之间的信息

mysql> select * from cwh where id between 2 and 4;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     | NULL |

+----+---------+------+

3 rows in set (0.00 sec)

9.查看表格打印age为空的信息

mysql> select * from cwh where age is null;

+----+------+------+

| id | name | age  |

+----+------+------+

|  4 | aaa  | NULL |

|  5 | bbb  | NULL |

|  6 | ccc  | NULL |

+----+------+------+

3 rows in set (0.00 sec)

10.查看表格打印age不为空的信息

mysql> select * from cwh where age is not null;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

+----+---------+------+

3 rows 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];

注意：此语句只能一条一条的修改记录，可以修改一条记录中的多个字段

1.修改表中的aaa的age由null改为40

mysql> update cwh set age=40 where name='aaa';

Query OK, 1 row affected (0.00 sec)

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     |   40 |

|  5 | bbb     | NULL |

|  6 | ccc     | NULL |

+----+---------+------+

6 rows in set (0.00 sec)

2.修改表中一行记录中多个字段将id=6的ccc改为cwh，age改为60

mysql> update cwh set name='cwh',age=60 where id=6;

Query OK, 1 row affected (0.00 sec)

Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     |   40 |

|  5 | bbb     | NULL |

|  6 | cwh     |   60 |

+----+---------+------+

6 rows 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];

1.删除某条记录

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     |   40 |

|  5 | bbb     | NULL |

|  6 | cwh     |   60 |

+----+---------+------+

6 rows in set (0.00 sec)

mysql> delete from cwh where id=5;

Query OK, 1 row affected (0.00 sec)

mysql> select * from cwh;

+----+---------+------+

| id | name    | age  |

+----+---------+------+

|  1 | tom     |   10 |

|  2 | jerry   |   20 |

|  3 | natasha |   30 |

|  4 | aaa     |   40 |

|  6 | cwh     |   60 |

+----+---------+------+

5 rows in set (0.00 sec)

2.删除整个表的内容

mysql> select * from cwh111;

+----+------+------+

| id | name | age  |

+----+------+------+

|  1 | qqq  |   10 |

|  2 | www  |   20 |

+----+------+------+

2 rows in set (0.00 sec)

mysql> delete from cwh111;

Query OK, 2 rows affected (0.00 sec)

mysql> select * from cwh111;

Empty 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

mysql> select * from cwh111;

+----+------+------+

| id | name | age  |

+----+------+------+

|  1 | qqq  |   10 |

|  2 | www  |   20 |

+----+------+------+

2 rows in set (0.00 sec)

mysql> truncate cwh111;

Query OK, 0 rows affected (0.01 sec)

mysql> select * from cwh111;

Empty 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。

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

1.授权cwh用户在数据库本机上登录访问所有数据库

mysql> grant all on *.* to cwh@127.0.0.1 identified by '+7p6Mg2JsHgX1bIaOSwSykG8O2M='; //此处密码使用openssl rand 20 -base64 生成

mysql> show grants for cwh@127.0.0.1

    -> ;

+--------------------------------------------------+

| Grants for cwh@127.0.0.1                         |

+--------------------------------------------------+

| GRANT ALL PRIVILEGES ON *.* TO 'cwh'@'127.0.0.1' |

+--------------------------------------------------+

1 row in set (0.00 sec)

2.授权cwh用户在192.168.112.149上远程登录访问chengweihong数据库

//首先授权

mysql> grant all on chengweihong.* to cwh@192.168.112.149 identifiied by '+7p6Mg2JsHgX1bIaOSwSykG8O2M=';

Query OK, 0 rows affected, 1 warning (0.00 sec)

//在查看授权内容

mysql> show grants for cwh@192.168.112.149;

+---------------------------------------------------------------------+

| Grants for cwh@192.168.112.149                                      |

+---------------------------------------------------------------------+

| GRANT USAGE ON *.* TO 'cwh'@'192.168.112.149'                       |

| GRANT ALL PRIVILEGES ON `chengweihong`.* TO 'cwh'@'192.168.112.149' |

+---------------------------------------------------------------------+

2 rows in set (0.00 sec)

//最后在192.168.112.149主机上验证

[root@146 ~]# mysql -ucwh -p -h192.168.112.146

Enter password: 

MySQL [(none)]> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| chengweihong       |

+--------------------+

2 rows in set (0.00 sec)

MySQL [chengweihong]> show tables;

+------------------------+

| Tables_in_chengweihong |

+------------------------+

| cwh                    |

| cwh111                 |

+------------------------+

2 rows in set (0.00 sec)

3.授权cwh用户在所有位置上远程登录访问chengweihong数据库的cwh表

//首先授权

mysql> grant all on chengweihong.cwh to 'cwh'@'%' identified by '+7p6Mg2JsHgX1bIaOSwSykG8O2M=';

Query OK, 0 rows affected, 1 warning (0.00 sec)

//在查看权限

mysql> show grants for cwh@'%';

+-----------------------------------------------------------+

| Grants for cwh@%                                          |

+-----------------------------------------------------------+

| GRANT USAGE ON *.* TO 'cwh'@'%'                           |

| GRANT ALL PRIVILEGES ON `chengweihong`.`cwh` TO 'cwh'@'%' |

+-----------------------------------------------------------+

2 rows in set (0.00 sec)

//在146主机上验证

[root@146 ~]# mysql -ucwh -p -h192.168.112.146

Enter password:

Welcome to the MariaDB monitor.  Commands end with ; or \g.

Your MySQL connection id is 11

Server version: 5.7.25 MySQL Community Server (GPL)

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

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

MySQL [(none)]> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| chengweihong       |

+--------------------+

2 rows in set (0.00 sec)

MySQL [(none)]> show tables from chengweihong;

+------------------------+

| Tables_in_chengweihong |

+------------------------+

| cwh                    |

+------------------------+

1 row in set (0.00 sec)

4.3.2 查看授权

1.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)

2.查看指定用户cwh的授权信息

mysql> show grants for cwh@'%';

+-----------------------------------------------------------+

| Grants for cwh@%                                          |

+-----------------------------------------------------------+

| GRANT USAGE ON *.* TO 'cwh'@'%'                           |

| GRANT ALL PRIVILEGES ON `chengweihong`.`cwh` TO 'cwh'@'%' |

+-----------------------------------------------------------+

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';

1.取消对cwh用户的授权

mysql> revoke all on chengweihong.cwh from cwh@'%';

Query OK, 0 rows affected (0.00 sec)

mysql> show grants for cwh@'%';

+---------------------------------+

| Grants for cwh@%                |

+---------------------------------+

| GRANT USAGE ON *.* TO 'cwh'@'%' |

+---------------------------------+

1 row in set (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

刷新授权表：

mysql> FLUSH PRIVILEGES;

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