MySQL基础

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摘要

数据结构模型主要有:关系模型:二维关系:row,columm数据库管理系统:关系:relational


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
  • 关键模型

关系模型:

二维关系:row,columm

数据库管理系统:

  • DBMS (DataBase Managment System)

关系:relational

关系型数据库管理系统:RDBMS

1.2 RDBMS专用名词

关系型数据库管理系统:

mysql:5.7版本之间都是开源 8.0后开始商业化

  • MySQL:MySQL,MariaDB,Percona-Server,sqlserver,MSsql(micresoft sql)
  • PostgreSQL:简称为pgsql
  • Oracle
  • MSSQL

非关系型数据库管理系统:

数据存放在内存当中 变量 key=value

  • mongodb
  • redis
  • memcache

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 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:
    • rpm:有两种
      • OS Vendor:操作系统发行商提供的
      • 项目官方提供的
    • deb

mysql安装步骤

[root@localhost ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm [root@localhost ~]# rpm -Uvh  mysql57-community-release-el7-11.noarch.rpm [root@localhost ~]# yum module disable mysql  //禁用mysql [root@localhost ~]# yum -y install mysql-community-server mysql-community-client  mysql-community-common mysql-community-devel  --nogpgcheck		//下载一个服务端,客户端,命令行,软件包			//--nogpgche禁止进行gpgcheck 

2.2 mysql配置

安装完后设置开机自启动

[root@localhost ~]# systemctl enable --now mysqld [root@localhost ~]# systemctl status mysqld ● mysqld.service - MySQL Server    Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)    Active: active (running) since Mon 2022-07-25 14:34:30 CST; 8s ago      Docs: man:mysqld(8)            http://dev.mysql.com/doc/refman/en/using-systemd.html   Process: 70174 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.p>   Process: 70022 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)  Main PID: 70176 (mysqld)     Tasks: 27 (limit: 23457)    Memory: 300.4M    CGroup: /system.slice/mysqld.service            └─70176 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid  Jul 25 14:34:28 localhost.localdomain systemd[1]: Starting MySQL Server... Jul 25 14:34:30 localhost.localdomain systemd[1]: Started MySQL Server.  

查看3306端口是否监听

[root@localhost ~]# ss -anlt | grep 3306 LISTEN 0      80                 *:3306            *:*           

在日志中找出密码

[root@localhost ~]# grep "password"  /var/log/mysqld.log  2022-07-25T06:34:28.883599Z 1 [Note] A temporary password is generated for root@localhost: OFU+amdhV3Wr			//临时密码 2022-07-25T06:35:33.642430Z 0 [Note] Shutting down plugin 'validate_password' 2022-07-25T06:35:34.759663Z 0 [Note] Shutting down plugin 'sha256_password' 2022-07-25T06:35:34.759665Z 0 [Note] Shutting down plugin 'mysql_native_password' 

使用临时密码登录MySQL

[root@localhost ~]# mysql -uroot -pOFU+amdhV3Wr		//-p后可以跟密码 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: 5.7.38  Copyright (c) 2000, 2022, 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> 				//看到这样的标识表示登录进去了 

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 '123456'; Query OK, 0 rows affected (0.00 sec) 

为避免mysql自动升级,需要卸载最开始安装的yum源

[root@localhost ~]# rpm -e mysql57-community-release 

3.mysql的层序组成

  • 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 //套接字     -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     -S 			//使用套接字连接,仅限于用于本地通讯 

示例

//查看当前MySQL的版本 [root@localhost ~]# mysql -V		 mysql  Ver 14.14 Distrib 5.7.38, for Linux (x86_64) using  EditLine wrapper  //指定服务器主机,默认为localhost,推荐使用ip地址 //套接字 [root@localhost ~]# mysql -uroot -p123456 -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 6 Server version: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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>   //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 -h127.0.0.1 Enter password:  Welcome to the MySQL monitor.  Commands end with ; or g. Your MySQL connection id is 7 Server version: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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>   //不登录mysql执行sql语句后退出,常用于脚本 [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 说明
ip socket 默认监听在tcp3306端口,支持远程通信
unix 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数据类型

MySQL中定义数据字段的类型对数据库的优化是非常重要的。MySQL支持多种类型,大致可以分为三类:数值、日期/时间和字符串(字符)类型。

4.1 数值类型

  • MySQL支持所有标准SQL数值数据类型。这些类型包括严格数值数据类型(INTEGER、SMALLINT、DECIMAL和NUMERIC),以及近似数值数据类型(FLOAT、REAL和DOUBLE PRECISION)。
  • 关键字INT是INTEGER的同义词,关键字DEC是DECIMAL的同义词。BIT数据类型保存位字段值,并且支持MyISAM、MEMORY、InnoDB和BDB表。作为SQL标准的扩展,MySQL也支持整数类型TINYINT、MEDIUMINT和BIGINT。下面的表显示了需要的每个整数类型的存储和范围
类型 大小 范围(有符号) 范围(无符号) 用途
TINYINT 1 byte (-128,127) (0,255) 小整数值
SMALLINT 2 bytes (-32 768,32 767) (0,65 535) 大整数值
MEDIUMINT 3 bytes (-8 388 608,8 388 607) (0,4 294 967 295) 大整数值
INT或INTEGER 4 bytes (-2 147 483 648,2 147 483 647) (0,4 294 967 295) 大整数值
BIGINT 8 bytes (-9,223,372,036,854,775,808,9 223 372 036 854 775 807) (0,18 446 744 073 709 551 615) 极大整数值
FLOAT 4 bytes (-3.402 823 466 E+38,-1.175 494 351 E-38),0,(1.175 494 351 E-38,3.402 823 466 351 E+38) 0,(1.175 494 351 E-38,3.402 823 466 E+38) 单精度
浮点数值
DOUBLE 8 bytes (-1.797 693 134 862 315 7 E+308,-2.225 073 858 507 201 4 E-308),0,(2.225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E+308) 0,(2.225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E+308) 双精度
浮点数值
DECIMAL 对DECIMAL(M,D) ,如果M>D,为M+2否则为D+2 依赖于M和D的值 依赖于M和D的值 小点数

4.2 日期和时间类型

  • 表示时间值的日期和时间类型为DATETIME、DATE、TIMESTAMP、TIME和YEAR。每个时间类型有一个有效值范围和一个"零"值,当指定不合法的MySQL不能表示的值时使用"零"值。TIMESTAMP类型有专有的自动更新特性,将在后面描述。
类型 大小(byte) 范围 格式 用途
DATE 3 1000-01-01/9999-12-31 YYYY-MM-DD 日期值
TIME 3 '-838:59:59'/'838:59:59' HH:MM:SS 时间值或持续时间
YEAR 1 1901/2155 YYYY 年份值
DATETIME 8 1000-01-01 00:00:00/9999-12-31 23:59:59 YYYY-MM-DD HH:MM:SS 混合日期和时间值
TIMESTAMP 4 1970-01-01 00:00:00/2038
结束时间是第 2147483647 秒,北京时间 2038-1-19 11:14:07,格林尼治时间 2038年1月19日 凌晨 03:14:07
YYYYMMDD HHMMSS 混合日期和时间值,时间戳

4.3 字符串类型

  • 字符串类型指CHAR、VARCHAR、BINARY、VARBINARY、BLOB、TEXT、ENUM和SET。该节描述了这些类型如何工作以及如何在查询中使用这些类型。
类型 大小 用途
CHAR 0-255 bytes 定长字符串
VARCHAR 0-65535 bytes 变长字符串
TINYBLOB 0-255 bytes 不超过 255 个字符的二进制字符串
TINYTEXT 0-255 bytes 短文本字符串
BLOB 0-65 535 bytes 二进制形式的长文本数据
TEXT 0-65 535 bytes 长文本数据
MEDIUMBLOB 0-16 777 215 bytes 二进制形式的中等长度文本数据
MEDIUMTEXT 0-16 777 215 bytes 中等长度文本数据
LONGBLOB 0-4 294 967 295 bytes 二进制形式的极大文本数据
LONGTEXT 0-4 294 967 295 bytes 极大文本数据

注意:char(n) 和 varchar(n) 中括号中 n 代表字符的个数,并不代表字节个数,比如 CHAR(30) 就可以存储 30 个字符。

  • CHAR 和 VARCHAR 类型类似,但它们保存和检索的方式不同。它们的最大长度和是否尾部空格被保留等方面也不同。在存储或检索过程中不进行大小写转换。
  • BINARY 和 VARBINARY 类似于 CHAR 和 VARCHAR,不同的是它们包含二进制字符串而不要非二进制字符串。也就是说,它们包含字节字符串而不是字符字符串。这说明它们没有字符集,并且排序和比较基于列值字节的数值值。
  • BLOB 是一个二进制大对象,可以容纳可变数量的数据。有 4 种 BLOB 类型:TINYBLOB、BLOB、MEDIUMBLOB 和 LONGBLOB。它们区别在于可容纳存储范围不同。
  • 有 4 种 TEXT 类型:TINYTEXT、TEXT、MEDIUMTEXT 和 LONGTEXT。对应的这 4 种 BLOB 类型,可存储的最大长度不同,可根据实际情况选择。

5.mysql数据库操作

5.1 DDL操作

5.1.1 数据库操作

创建数据库

[root@localhost ~]# mysql -uroot -p		//先进入MySQL数据库 Enter password:  Welcome to the MySQL monitor.  Commands end with ; or g. Your MySQL connection id is 10 Server version: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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> show databases;		//查看数据库 +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | +--------------------+ 4 rows in set (0.00 sec) 	 mysql> create database zxr;				//创建数据库 Query OK, 1 row affected (0.00 sec)  mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | | zxr                | +--------------------+ 5 rows in set (0.00 sec) 

删除数据库

mysql> show databases;					//查看数据库 +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | | zxr                | +--------------------+ 5 rows in set (0.00 sec)  mysql> drop database zxr;				//删除数据库 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)  

5.1.2 表操作

创建表之前需要进入一个数据库

mysql> create database zxr;			//需要先创建一个数据库 Query OK, 1 row affected (0.00 sec)  mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | | zxr                | +--------------------+ 5 rows in set (0.00 sec)  mysql> use zxr;		//进入数据库里 Database changed	//进入成功  mysql> create table linux (id int not null ,name varchar(100) not null,age tinyint);		//创建表 Query OK, 0 rows affected (0.01 sec)  mysql> show tables;			//查看表 +---------------+ | Tables_in_zxr | +---------------+ | linux         | +---------------+ 1 row in set (0.00 sec) 

删除表

mysql> show tables; +---------------+ | Tables_in_zxr | +---------------+ | linux         | +---------------+ 1 row in set (0.00 sec)  mysql> drop table linux;			//drop删除 Query OK, 0 rows affected (0.00 sec)  mysql> show tables; Empty set (0.00 sec) 

5.1.3 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

host值可以为

  • IP地址,如127.0.0.1
  • 通配符
    • %:配置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

创建用户

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

[root@localhost ~]# mysql -uroot -p Enter password:  Welcome to the MySQL monitor.  Commands end with ; or g. Your MySQL connection id is 12 Server version: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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> create user 'zxr'@'127.0.0.1' identified by '123456';	//创建用户 Query OK, 0 rows affected (0.00 sec) 

使用新创建的用户和密码登录mysql

[root@localhost ~]# mysql -uzxr -p123456 -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: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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>  

删除用户

[root@localhost ~]# mysql -uroot -p Enter password:  Welcome to the MySQL monitor.  Commands end with ; or g. Your MySQL connection id is 14 Server version: 5.7.38 MySQL Community Server (GPL)  Copyright (c) 2000, 2022, 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> drop user 'zxr'@'127.0.0.1';			//删除用户 Query OK, 0 rows affected (0.00 sec)  mysql>  

4.1.4 查看命令show

查看支持的所有字符

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 | 

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) 

查看数据库信息

mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | | zxr                | +--------------------+ 5 rows in set (0.01 sec) 

不进入数据库而列出其包含的所有表

mysql> show tables from zxr; +---------------+ | Tables_in_zxr | +---------------+ | linux         | +---------------+ 1 row in set (0.00 sec) 

查看表结构

mysql> desc zxr.linux; +-------+--------------+------+-----+---------+-------+ | 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) 

查看表的创建命令

mysql> show create table zxr.linux; +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table                                                                                                                                           | +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+ | linux | CREATE TABLE `linux` (   `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) 

查看表的状态

mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mysql              | | performance_schema | | sys                | | zxr                | +--------------------+ 5 rows in set (0.00 sec)  mysql> use zxr;		//进入数据库 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 mysql> show table status like 'linux'G *************************** 1. row ***************************            Name: linux          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: 2022-07-25 16:00:38     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 如何获取帮助

语法:HELP keyword;

示例

mysql> help create database; Name: 'CREATE DATABASE' Description: Syntax: CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name     [create_option] ...  create_option: [DEFAULT] {     CHARACTER SET [=] charset_name   | COLLATE [=] collation_name }  CREATE DATABASE creates a database with the given name. To use this statement, you need the CREATE privilege for the database. CREATE SCHEMA is a synonym for CREATE DATABASE.  URL: https://dev.mysql.com/doc/refman/5.7/en/create-database.html