mysql
2022/7/26 2:22:47
本文主要是介绍mysql，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！
mysql
- 1. mysql数据库基础
- 1.1数据库
- 1.1.1常见的数据库
- 1.1.2数据库结构模型
- 1.1.3 数据库管理系统
- 1.1.4常见的关系型数据库管理系统
- 1.1.5 关系型数据库的常见组件
- 1.1数据库
- 2. SQL语句
- 2.1 mysql安装
- 2.1.1 mysql方式
- 2.2.2mysql配置
- 2.2.3 mysql的程序组成
- 2.2.4 mysql工具使用
- 2.2.5 服务器监听的两种socket地址
- 2.1 mysql安装
- 3. mysql数据库操作
- 3.1 DDL操作
- 3.1.1 数据库操作
- 3.1.2 表操作
- 3.1.3 用户操作
- 3.1.4 查看命令show
- 3.1 DDL操作
- 4. MySQL数据类型
1. mysql数据库基础
1.1数据库
1.1.1常见的数据库
-
关系型数据库：数据存放在硬盘当中
字段：每一列的第一行就是字段
记录：每一行代表一条记录- mysql（5.7之前都是开源，8.0开始商业化）
- mariadb -->10.0
- MSsql MicreSoft Sql
- Oracle 商业软件
- sqlserver
-
非关系型数据库：数据存放在内存当中，变量，key=value
- mongodb
- redis
- memcache
-
sqlite：数据存放在文件当中 sql
1.1.2数据库结构模型
- 层次模型
- 网状结构
- 关系模型
1.1.3 数据库管理系统
数据库管理系统：DBMS DateBase Managment System mysql
关系：Relational，RDBMS
Relationship 关系
RDBMS 关系数据库系统
1.1.4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
1.1.5 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
2. 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 |
2.1 mysql安装
2.1.1 mysql方式
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
- rpm：有两种
- deb
[root@mr ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm --2022-07-25 17:42:52-- http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm Resolving dev.mysql.com (dev.mysql.com)... 23.2.135.207, 2600:1402:3800:2ab::2e31, 2600:1402:3800:28b::2e31 Connecting to dev.mysql.com (dev.mysql.com)|23.2.135.207|:80... connected. HTTP request sent, awaiting response... 301 Moved Permanently Location: https://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm [following] --2022-07-25 17:42:52-- https://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm Connecting to dev.mysql.com (dev.mysql.com)|23.2.135.207|:443... connected. HTTP request sent, awaiting response... 302 Moved Temporarily Location: https://repo.mysql.com//mysql57-community-release-el7-11.noarch.rpm [following] --2022-07-25 17:42:53-- https://repo.mysql.com//mysql57-community-release-el7-11.noarch.rpm Resolving repo.mysql.com (repo.mysql.com)... 184.27.29.58 Connecting to repo.mysql.com (repo.mysql.com)|184.27.29.58|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 25680 (25K) [application/x-redhat-package-manager] Saving to: ‘mysql57-community-release-el7-11.noarch.rpm’ mysql57-community-releas 100%[================================>] 25.08K 167KB/s in 0.2s 2022-07-25 17:42:53 (167 KB/s) - ‘mysql57-community-release-el7-11.noarch.rpm’ saved [25680/25680] [root@mr ~]# ls 123 htop-1.0.2 sleep 2 htop-1.0.2.tar.gz wget-1.14-18.el7_6.1.x86_64.rpm a mysql57-community-release-el7-11.noarch.rpm wget-1.19.5-10.el8.x86_64.rpm abc nohup.out xixi hehe outfile [root@mr ~]# rpm -Uvh mysql57-community-release-el7-11.noarch.rpm warning: mysql57-community-release-el7-11.noarch.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY Verifying... ################################# [100%] Preparing... ################################# [100%] Updating / installing... 1:mysql57-community-release-el7-11 ################################# [100%] [root@mr ~]# [root@mr ~]# ls /etc/yum.repos.d/ CentOS-Stream-AppStream.repo CentOS-Stream-HighAvailability.repo mysql-community.repo CentOS-Stream-BaseOS.repo CentOS-Stream-Media.repo mysql-community-source.repo CentOS-Stream-Debuginfo.repo CentOS-Stream-PowerTools.repo CentOS-Stream-Extras.repo CentOS-Stream-RealTime.repo [root@mr ~]# [root@mr ~]# yum module disable mysql Last metadata expiration check: 0:03:45 ago on Mon 25 Jul 2022 05:46:28 PM CST. Dependencies resolved. ================================================================================================== Package Architecture Version Repository Size ================================================================================================== Disabling modules: mysql Transaction Summary ================================================================================================== Is this ok [y/N]: y Complete! [root@mr ~]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel --nogpgcheck Last metadata expiration check: 0:04:07 ago on Mon 25 Jul 2022 05:46:28 PM CST. Dependencies resolved. ================================================================================================== Package Arch Version Repository Size ================================================================================================== Installing: mysql-community-client x86_64 5.7.38-1.el7 mysql57-community 28 M mysql-community-common x86_64 5.7.38-1.el7 mysql57-community 311 k mysql-community-devel x86_64 5.7.38-1.el7 mysql57-community 4.2 M mysql-community-server x86_64 5.7.38-1.el7 mysql57-community 178 M Installing dependencies: mysql-community-libs x86_64 5.7.38-1.el7 mysql57-community 2.6 M ncurses-compat-libs x86_64 6.1-9.20180224.el8 baseos 328 k net-tools x86_64 2.0-0.52.20160912git.el8 baseos 322 k Transaction Summary ================================================================================================== Install 7 Packages Total download size: 213 M Installed size: 916 M Downloading Packages: (1/7): net-tools-2.0-0.52.20160912git.el8.x86_64.rpm 787 kB/s | 322 kB 00:00 (2/7): ncurses-compat-libs-6.1-9.20180224.el8.x86_64.rpm 506 kB/s | 328 kB 00:00 (3/7): mysql-community-common-5.7.38-1.el7.x86_64.rpm 143 kB/s | 311 kB 00:02 (4/7): mysql-community-devel-5.7.38-1.el7.x86_64.rpm 2.1 MB/s | 4.2 MB 00:02 (5/7): mysql-community-libs-5.7.38-1.el7.x86_64.rpm 832 kB/s | 2.6 MB 00:03 (6/7): mysql-community-client-5.7.38-1.el7.x86_64.rpm 4.2 MB/s | 28 MB 00:06 (7/7): mysql-community-server-5.7.38-1.el7.x86_64.rpm 7.9 MB/s | 178 MB 00:22 -------------------------------------------------------------------------------------------------- Total 8.3 MB/s | 213 MB 00:25 Running transaction check Transaction check succeeded. Running transaction test Transaction test succeeded. Running transaction Preparing : 1/1 Installing : mysql-community-common-5.7.38-1.el7.x86_64 1/7 Installing : mysql-community-libs-5.7.38-1.el7.x86_64 2/7 Running scriptlet: mysql-community-libs-5.7.38-1.el7.x86_64 2/7 Installing : net-tools-2.0-0.52.20160912git.el8.x86_64 3/7 Running scriptlet: net-tools-2.0-0.52.20160912git.el8.x86_64 3/7 Installing : ncurses-compat-libs-6.1-9.20180224.el8.x86_64 4/7 Installing : mysql-community-client-5.7.38-1.el7.x86_64 5/7 Running scriptlet: mysql-community-server-5.7.38-1.el7.x86_64 6/7 Installing : mysql-community-server-5.7.38-1.el7.x86_64 6/7 Running scriptlet: mysql-community-server-5.7.38-1.el7.x86_64 6/7 Installing : mysql-community-devel-5.7.38-1.el7.x86_64 7/7 Running scriptlet: mysql-community-devel-5.7.38-1.el7.x86_64 7/7 [/usr/lib/tmpfiles.d/mysql.conf:23] Line references path below legacy directory /var/run/, updating /var/run/mysqld → /run/mysqld; please update the tmpfiles.d/ drop-in file accordingly. Verifying : ncurses-compat-libs-6.1-9.20180224.el8.x86_64 1/7 Verifying : net-tools-2.0-0.52.20160912git.el8.x86_64 2/7 Verifying : mysql-community-client-5.7.38-1.el7.x86_64 3/7 Verifying : mysql-community-common-5.7.38-1.el7.x86_64 4/7 Verifying : mysql-community-devel-5.7.38-1.el7.x86_64 5/7 Verifying : mysql-community-libs-5.7.38-1.el7.x86_64 6/7 Verifying : mysql-community-server-5.7.38-1.el7.x86_64 7/7 Installed products updated. Installed: mysql-community-client-5.7.38-1.el7.x86_64 mysql-community-common-5.7.38-1.el7.x86_64 mysql-community-devel-5.7.38-1.el7.x86_64 mysql-community-libs-5.7.38-1.el7.x86_64 mysql-community-server-5.7.38-1.el7.x86_64 ncurses-compat-libs-6.1-9.20180224.el8.x86_64 net-tools-2.0-0.52.20160912git.el8.x86_64 Complete! [root@mr ~]#
2.2.2mysql配置
yum安装
[root@mr ~]# systemctl enable --now mysqld（设置开机自启）
[root@mr ~]# 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 17:56:50 CST; 8s ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 7107 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYS>
Process: 7057 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 7109 (mysqld)
Tasks: 27 (limit: 12221)
Memory: 311.3M
CGroup: /system.slice/mysqld.service
└─7109 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
Jul 25 17:56:48 mr systemd[1]: Starting MySQL Server...
Jul 25 17:56:50 mr systemd[1]: Started MySQL Server.
[root@mr ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 0.0.0.0:111 0.0.0.0:*
LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
LISTEN 0 25 0.0.0.0:514 0.0.0.0:*
LISTEN 0 80 *:3306 *:*
LISTEN 0 128 [::]:111 [::]:*
LISTEN 0 128 [::]:22 [::]:*
LISTEN 0 25 [::]:514 [::]:*
[root@mr ~]# grep "password" /var/log/mysqld.log
2022-07-25T09:56:48.633177Z 1 [Note] A temporary password is generated for root@localhost: 9MS,WsyWhp>#
[root@mr ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.38
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> 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> set password = password('123456');
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> exit
Bye
[root@mr ~]# mysql -uroot -p'123456'
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 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> exit
Bye
[root@mr ~]# rpm -qa | grep mysql
mysql57-community-release-el7-11.noarch
[root@mr ~]# rpm -e mysql57-community-release-el7-11.noarch
[root@mr ~]#
yum安装mariadb:
- 1.yum install -y mariadb*
-
- systemctl enable --now mariadb
-
- mysql
-
- set password = password('xxxx');
-
- exit
-
- mysql -uroot -pxxxx
2.2.3 mysql的程序组成
- 客户端
- mysql：CLI交互式客户端程
- 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
[root@mr ~]# mysql_secure_installation Securing the MySQL server deployment. Enter password for user root: 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: 0 Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : y ... Failed! Error: Your password does not satisfy the current policy requirements New password: Re-enter new password: Estimated strength of the password: 50 Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : y 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 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 ... 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 - 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 Success. All done! [root@mr ~]# [root@mr ~]# mysql -uroot -pmarui 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 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> [root@mr ~]# ps aux | grep mysqld mysql 7109 0.0 9.5 1383676 189808 ? Sl 17:56 0:04 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid root 7373 0.0 0.0 12144 1168 pts/0 S+ 21:08 0:00 grep --color=auto mysqld [root@mr ~]#
2.2.4 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@mr ~]# mysql -V mysql Ver 14.14 Distrib 5.7.38, for Linux (x86_64) using EditLine wrapper [root@mr ~]# mysql -uroot -pmarui -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 11 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> exit Bye [root@mr ~]# mysql -uroot -pmarui -e 'show databases;' mysql: [Warning] Using a password on the command line interface can be insecure. +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ [root@mr ~]#
2.2.5 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 |
3. mysql数据库操作
3.1 DDL操作
3.1.1 数据库操作
[root@mr ~]# mysql -uroot -pmarui 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> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.00 sec) mysql> create database runtime; Query OK, 1 row affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | runtime | | sys | +--------------------+ 5 rows in set (0.00 sec) mysql> drop database runtime; Query OK, 0 rows affected (0.01 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.00 sec) mysql>
3.1.2 表操作
mysql> create table Linux(id int not null,name varchar(10),age tinyint (2)); Query OK, 0 rows affected (0.01 sec) mysql> desc Linux; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int(11) | NO | | NULL | | | name | varchar(10) | YES | | NULL | | | age | tinyint(2) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 3 rows in set (0.00 sec) mysql> select * from Linux; Empty set (0.00 sec) mysql> show tables; +-------------------+ | Tables_in_runtime | +-------------------+ | Linux | +-------------------+ 1 row in set (0.00 sec) mysql> drop table Linux; Query OK, 0 rows affected (0.01 sec) mysql> show tables; Empty set (0.00 sec) mysql>
3.1.3 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
mysql> create user 'tom'@'mr' identified by 'marui'; Query OK, 0 rows affected (0.00 sec) mysql> drop user 'tom'@'mr'; Query OK, 0 rows affected (0.00 sec) mysql> select * from mysql.user; +-----------+---------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+-----------------------+-------------------------------------------+------------------+-----------------------+-------------------+----------------+ | Host | User | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_slave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | Create_tablespace_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max_updates | max_connections | max_user_connections | plugin | authentication_string | password_expired | password_last_changed | password_lifetime | account_locked | +-----------+---------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+-----------------------+-------------------------------------------+------------------+-----------------------+-------------------+----------------+ | localhost | root | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | mysql_native_password | *9370E4584BA357054A156F3EF8CBCE33FBAB4BF3 | N | 2022-07-25 21:03:40 | NULL | N | | localhost | mysql.session | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | Y | N | N | N | N | N | N | N | N | N | N | N | N | N | | | | | 0 | 0 | 0 | 0 | mysql_native_password | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | N | 2022-07-25 17:56:48 | NULL | Y | | localhost | mysql.sys | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | | | | | 0 | 0 | 0 | 0 | mysql_native_password | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | N | 2022-07-25 17:56:48 | NULL | Y | +-----------+---------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+-----------------------+-------------------------------------------+------------------+-----------------------+-------------------+----------------+ 3 rows in set (0.00 sec) mysql>
3.1.4 查看命令show
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 (0.00 sec) mysql> 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) mysql> mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | runtime | | sys | +--------------------+ 5 rows in set (0.00 sec) mysql> show tables from runtime; Empty set (0.00 sec) mysql>
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。
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 | 1byte | （-128,127） | （0,255） | 小整数值 |
| SMALLINT | 2 bytes | (-32 768， 32 767) | (O.65 535) | 大整数值 |
| MEDIUMINT | 3 bytes | (-8388 608， 8 388 607) | (O，16 777215) | 大整数值 |
| INT或INTEGER | 4 bytes | (-2147 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 |
| LOAT | 4 bytes | (-3.402 823 466 E+38， -1.175 494351E-38），（1.175 494 351 E-38，3.402 832 466 351 E+38） | 0, (1 175494351 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 858507 201 4 E-308)，0，1.797 693 134 862 315 7 E+308) | 0， (2 .225 073 858 507 201 4 E-308） | (2.225 073 858507 2014 E-308， 1.797 693 134 862 315 7 E+308) |
| 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 | 小数值 |
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( bytes) | 范围 | 格式 | 用途 |
|---|---|---|---|---|
| DATE | 3 | 1000-01-019999-12-31 | YYY-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 | 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 |
| TIMESTA MP | 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 | YYYYMMDDHHMMSS | 混合日期和时间值,时间戳 |
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，并不代表宇节个数，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宇符串而不要非二进制宇符串。也就
是说，它们包含字节字符串而不是字符宇符串。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。
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