mysql基础
1.关系型数据库的介绍
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语句的类型 | 对应操作 |
|---|---|
| DDL | create：创建 drop：删除 alter：修改 |
| DML | insert：向表中插入数据 delete：删除表中的数据 update：更新表中的数据 select：查询表中的数据 |
| DCL | grant：授权 revoke：移除授权 |
2.MySQL的安装与配置
2.1 安装mysql
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
- rpm：有两种
使用yum安装mysql
#配置mysql的yum源
[root@zzd139 ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm
[root@zzd139 ~]# 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%]
#将yum仓库自带的mysql先禁用掉
[root@zzd139 ~]# dnf module disable mysql
#安装mysql5.7
[root@zzd139 ~]# dnf -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel --nogpgcheck
2.2 mysql配置
#将mysql设置为开机自启并且启动mysql
[root@zzd139 ~]# systemctl enable --now mysqld
[root@zzd139 ~]# 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 17:41:45 CST; 7s ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 4357 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Process: 4308 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 4360 (mysqld)
Tasks: 27 (limit: 5770)
Memory: 291.9M
CGroup: /system.slice/mysqld.service
└─4360 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
Jul 25 17:41:42 zzd139 systemd[1]: Starting MySQL Server...
Jul 25 17:41:45 zzd139 systemd[1]: Started MySQL Server.
#查看端口号
[root@zzd139 ~]# ss -antlp | grep mysql
LISTEN 0 80 *:3306 *:* users:(("mysqld",pid=4360,fd=21))
#获取mysql的初始密码
[root@zzd139 ~]# cat /var/log/mysqld.log | grep password
2022-07-25T09:41:43.449315Z 1 [Note] A temporary password is generated for root@localhost: haaforZyu7-k
2022-07-25T09:43:00.066543Z 2 [Note] Access denied for user 'root'@'localhost' (using password: NO)
#使用初始密码登录到mysql命令行
[root@zzd139 ~]# mysql -uroot -p
Enter password:
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>
#修改mysql的密码
mysql> set global validate_password_policy=0; //更改mysql的密码等级
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_length=1; //更改mysql的密码长度
Query OK, 0 rows affected (0.00 sec)
mysql> set password = password('zzd123!!'); //更改mysql的密码
Query OK, 0 rows affected, 1 warning (0.00 sec)
#退出mysql
mysql> exit;
Bye
#为了避免后期mysql自动升级，将最开始的yum源卸载
[root@zzd139 ~]# rpm -e mysql57-community-release
2.3 mariadb安装
dnf -y install mariadb*
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工具的使用
语法：mysql [OPTIONS] [database]
常用选项(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
-pHOSTpassword 指定用户密码
-P 指定数据库监听端口
-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@zzd139 ~]# mysql -uroot -p
#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@zzd139 ~]# mysql -uroot -pzzd123 -hlocalhost
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 16
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@zzd139 ~]# mysql -V
mysql Ver 14.14 Distrib 5.7.38, for Linux (x86_64) using EditLine wrapper
[root@zzd139 ~]# mysql -uroot -pzzd123 -e 'show databases;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| 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 | 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) | (0，16 777 215) | 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DECI MAL(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 | 1000-01-01/9999-12-31 | 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 |
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 |
5.mysql数据库操作
5.1DDL语句
5.1.1 数据库操作
#创建数据库
mysql> create database zic;
Query OK, 1 row affected (0.00 sec)
#查看当前有哪些数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| zic |
+--------------------+
5 rows in set (0.00 sec)
#删除数据库
mysql> drop database zic;
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
mysql> create database zic; #创建数据库
Query OK, 1 row affected (0.00 sec)
mysql> use zic; #进入数据库
Database changed
mysql> create table zzd(id int not null,name varchar(20),sex varchar(3)); #创建表
Query OK, 0 rows affected (0.01 sec)
#查看当前数据库有哪些表
mysql> show tables;
+---------------+
| Tables_in_zic |
+---------------+
| zzd |
+---------------+
1 row in set (0.00 sec)
#删除表
mysql> drop table zzd;
Query OK, 0 rows affected (0.01 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
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
#创建用户
mysql> create user zic@'localhost' identified by 'zic123456';
Query OK, 0 rows affected (0.00 sec)
#使用上面创建的用户登录mysql
[root@zzd139 ~]# mysql -uzic -pzic123456 -hlocalhost;
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 20
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
mysql> drop user zic@'localhost';
Query OK, 0 rows affected (0.00 sec)
5.1.4 查看命令show
#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 (0.00 sec)
#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)
#上一条命令显示的比较乱，可以使用\G来以列的方式显示
mysql> show engines\G;
*************************** 1. row ***************************
Engine: InnoDB
Support: DEFAULT
Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
XA: YES
Savepoints: YES
*************************** 2. row ***************************
Engine: MRG_MYISAM
Support: YES
Comment: Collection of identical MyISAM tables
Transactions: NO
XA: NO
Savepoints: NO
*************************** 3. row ***************************
Engine: MEMORY
Support: YES
Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
XA: NO
Savepoints: NO
…………
#查看数据库信息
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| zic |
+--------------------+
5 rows in set (0.00 sec)
#不进入某数据库而列出其包含的所有表
mysql> show tables from zic;
+---------------+
| Tables_in_zic |
+---------------+
| zzd |
+---------------+
1 row in set (0.00 sec)
#查看表的结构
mysql> desc zzd;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(20) | YES | | NULL | |
| sex | varchar(3) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
#查看zzd表的创建过程
mysql> show create table zzd;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
| zzd | CREATE TABLE `zzd` (
`id` int(11) NOT NULL,
`name` varchar(20) DEFAULT NULL,
`sex` varchar(3) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
#查看zzd表的状态
mysql> show table status like 'zzd'\G;
*************************** 1. row ***************************
Name: zzd
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 21:41:13
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
5.1.5获取帮助
#获取创建数据库的帮助
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
5.2 DML操作
DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。
5.2.1 insert语句
#向表zzd中插入数据
mysql> use zic;
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> insert into zzd(id,name,sex) values(1,'zhangsan','M'),(2,'lisi','W'),(3,'wangwu','M'),(4,'lisa','W');
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
5.2.2 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，当表明很长时用别名代替 |
#查看zzd表的所有字段
mysql> select * from zzd;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+----------+------+
4 rows in set (0.00 sec)
#查看表zzd的name和sex字段，并且分别用“姓名”和“性别”做别名代替
mysql> select name as 姓名,sex as 性别 from zzd;
+----------+--------+
| 姓名 | 性别 | $(这种别名替换只是临时的，下次执行select就没了)
+----------+--------+
| zhangsan | M |
| lisi | W |
| wangwu | M |
| lisa | W |
+----------+--------+
4 rows in set (0.00 sec)
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 |
#使用where判断语句查询zzd表中id大于2的记录
mysql> select * from zzd where id > 2;
+----+--------+------+
| id | name | sex |
+----+--------+------+
| 3 | wangwu | M |
| 4 | lisa | W |
+----+--------+------+
2 rows in set (0.01 sec)
#使用where判断语句查询zzd表中id小于4的记录
mysql> select * from zzd where id < 4;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
| 3 | wangwu | M |
+----+----------+------+
3 rows in set (0.00 sec)
#使用where判断语句查询zzd表中id大于等于2的记录
mysql> select * from zzd where id >= 2;
+----+--------+------+
| id | name | sex |
+----+--------+------+
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+--------+------+
3 rows in set (0.00 sec)
#使用where判断语句查询zzd表中id小于等于2的记录
mysql> select * from zzd where id <= 2;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
+----+----------+------+
2 rows in set (0.00 sec)
#使用where判断语句查询zzd表中name等于'lisa'的记录
mysql> select * from zzd where name = 'lisa';
+----+------+------+
| id | name | sex |
+----+------+------+
| 4 | lisa | W |
+----+------+------+
1 row in set (0.01 sec)
#使用where判断语句查询zzd表中id字段的范围在2——4之间的记录
mysql> select * from zzd where id between 2 and 4;
+----+--------+------+
| id | name | sex |
+----+--------+------+
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+--------+------+
3 rows in set (0.00 sec)
#模糊查找表zzd中匹配'%g%'的的记录
mysql> select * from zzd where name like '%g%';
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 3 | wangwu | M |
+----+----------+------+
2 rows in set (0.00 sec)
#查询表zzd中name字段不为空的记录
mysql> select * from zzd where name is not null;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+----------+------+
4 rows in set (0.00 sec)
#查询表zzd中name字段为空的记录
mysql> select * from zzd where name is null;
Empty set (0.00 sec)
#查询表zzd中id字段为等于2并且name字段为'lisi'的记录
mysql> select * from zzd where id = 2 and name = 'lisi';
+----+------+------+
| id | name | sex |
+----+------+------+
| 2 | lisi | W |
+----+------+------+
1 row in set (0.00 sec)
#查询表zzd中id字段为等于4或者name字段为'lisi'的记录
mysql> select * from zzd where id = 4 or name = 'lisi';
+----+------+------+
| id | name | sex |
+----+------+------+
| 2 | lisi | W |
| 4 | lisa | W |
+----+------+------+
2 rows in set (0.00 sec)
#查询zzd表name字段不是'zhangsan'的字段
mysql> select * from zzd where not name = 'zhangsan'
-> ;
+----+--------+------+
| id | name | sex |
+----+--------+------+
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+--------+------+
3 rows in set (0.00 sec)
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 |
#对zzd表以字段id进行升序排序
mysql> select * from zzd order by id;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
| 3 | wangwu | M |
| 4 | lisa | W |
+----+----------+------+
4 rows in set (0.00 sec)
#对zzd表以字段id进行降序排序
mysql> select * from zzd order by id desc;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 4 | lisa | W |
| 3 | wangwu | M |
| 2 | lisi | W |
| 1 | zhangsan | M |
+----+----------+------+
4 rows in set (0.00 sec)
#对zzd表以字段id进行升序排序只去前两条记录
mysql> select * from zzd order by id limit 2;
+----+----------+------+
| id | name | sex |
+----+----------+------+
| 1 | zhangsan | M |
| 2 | lisi | W |
+----+----------+------+
2 rows in set (0.00 sec)
#对zzd表以字段id进行逆序排序并略过前两条记录，取后面后面一条记录，也就是第三条记录
mysql> select * from zzd order by id desc limit 2,1;
+----+------+------+
| id | name | sex |
+----+------+------+
| 2 | lisi | W |
+----+------+------+
1 row in set (0.00 sec)
5.2.3 update语句
#给表zzd新添加一个字段idnum
mysql> alter table zzd add idnum varchar(20);
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc zzd;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(20) | YES | | NULL | |
| sex | varchar(3) | YES | | NULL | |
| idnum | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
mysql> select * from zzd;
+----+----------+------+-------+
| id | name | sex | idnum |
+----+----------+------+-------+
| 1 | zhangsan | M | NULL |
| 2 | lisi | W | NULL |
| 3 | wangwu | M | NULL |
| 4 | lisa | W | NULL |
+----+----------+------+-------+
4 rows in set (0.00 sec)
#将表zzd中name为'zhangsan'的idnum字段改为‘123456'
mysql> update zzd set idnum = '123456' where name = 'zhangsan';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from zzd;
+----+----------+------+--------+
| id | name | sex | idnum |
+----+----------+------+--------+
| 1 | zhangsan | M | 123456 |
| 2 | lisi | W | NULL |
| 3 | wangwu | M | NULL |
| 4 | lisa | W | NULL |
+----+----------+------+--------+
4 rows in set (0.01 sec)
5.2.4 delete语句
#创建zzdtest表，有字段id，name，age，id字段为主键并且自动增长
mysql> create table zzdtest(id int not null primary key auto_increment,name varchar(20),age tinyint);
Query OK, 0 rows affected (0.01 sec)
mysql> desc zzdtest;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
#插入几条数据，id字段不用管
mysql> insert into zzdtest(name,age) values('lisa',18),('tom',19),('jreey',18),('natasha',20);
Query OK, 4 rows affected (0.01 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select * from zzdtest;
+----+---------+------+
| id | name | age |
+----+---------+------+
| 1 | lisa | 18 | $(id字段自动增长)
| 2 | tom | 19 |
| 3 | jreey | 18 |
| 4 | natasha | 20 |
+----+---------+------+
4 rows in set (0.00 sec)
#删除name为'tom'的记录
mysql> delete from zzdtest where name = 'tom';
Query OK, 1 row affected (0.00 sec)
mysql> select * from zzdtest;
+----+---------+------+
| id | name | age |
+----+---------+------+
| 1 | lisa | 18 |
| 3 | jreey | 18 |
| 4 | natasha | 20 |
+----+---------+------+
3 rows in set (0.00 sec)
#删除整张表的所有记录
mysql> delete from zzdtest;
Query OK, 3 rows affected (0.00 sec)
mysql> select * from zzdtest;
Empty set (0.00 sec)
$(只是删除了表的记录，并没有删除表或表的结构)
mysql> desc zzdtest;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
5.2.5 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 |
#重新对zzdtest表插入数据
mysql> insert into zzdtest(name,age) values('lisa',18),('tom',19),('jreey',18),('natasha',20);
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select * from zzdtest;
$(id是自动增长，但是是从5开始的，这是用为delete删除并没有完全删除，而是会存在与日志中，后面可以恢复，所以不会重置自动增长)
+----+---------+------+
| id | name | age |
+----+---------+------+
| 5 | lisa | 18 |
| 6 | tom | 19 |
| 7 | jreey | 18 |
| 8 | natasha | 20 |
+----+---------+------+
4 rows in set (0.00 sec)
#删除zzdtest表中的所有记录
mysql> truncate zzdtest;
Query OK, 0 rows affected (0.01 sec)
mysql> select * from zzdtest;
Empty set (0.00 sec)
#重新再插入数据
mysql> insert into zzdtest(name,age) values('lisa',18),('tom',19),('jreey',18),('natasha',20);
Query OK, 4 rows affected (0.01 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select * from zzdtest;
$(truncate删除是不可恢复的，会重置自动增长，所以truncate语句删除需要慎用)
+----+---------+------+
| id | name | age |
+----+---------+------+
| 1 | lisa | 18 |
| 2 | tom | 19 |
| 3 | jreey | 18 |
| 4 | natasha | 20 |
+----+---------+------+
4 rows in set (0.00 sec)
5.3 DCL操作
5.3.1 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。
#授权zzd用户在数据库本机上登录访问所有数据库
mysql> grant all on *.* to zzd@'localhost' identified by 'zzd123';
Query OK, 0 rows affected, 1 warning (0.00 sec)
#刷新授权
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
#查看zzd@'localhost'的授权
mysql> show grants for zzd@'localhost';
+--------------------------------------------------+
| Grants for zzd@localhost |
+--------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'zzd'@'localhost' |
+--------------------------------------------------+
1 row in set (0.00 sec)
#使用用户zzd@'localhost'登录mysql
[root@zzd139 ~]# mysql -uzzd -p -hlocalhost
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
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>
5.3.2 取消授权revoke
#取消zzd用户在数据库本机上登录访问所有数据库的权限
mysql> revoke all on *.* from zzd@'localhost';
Query OK, 0 rows affected (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
#查看授权
mysql> show grants for zzd@'localhost';
+-----------------------------------------+
| Grants for zzd@localhost |
+-----------------------------------------+
| GRANT USAGE ON *.* TO 'zzd'@'localhost' |
+-----------------------------------------+
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
mysql> FLUSH PRIVILEGES;
mysql远程连接工具
#新建一个用户zzd@'192.168.169.1'对所有数据库拥有所有权限
mysql> grant all on *.* to zzd@'192.168.169.1' identified by 'zzdlink';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
打开远程连接工具，新建连接
点击测试连接，显示连接成功，可点击确定进行连接
实战案例
1.搭建mysql服务
#配置mysql的yum源
[root@zzd139 ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm
[root@zzd139 ~]# 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%]
#将yum仓库自带的mysql先禁用掉
[root@zzd139 ~]# dnf module disable mysql
#安装mysql5.7
[root@zzd139 ~]# dnf -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel --nogpgcheck
[root@zzd139 ~]# cat /var/log/mysqld.log | grep password
2022-07-25T09:41:43.449315Z 1 [Note] A temporary password is generated for root@localhost: haaforZyu7-k
2022-07-25T09:43:00.066543Z 2 [Note] Access denied for user 'root'@'localhost' (using password: NO)
#使用查找到的密码登录mysql
[root@zzd139 ~]# mysql -uroot -p
Enter password:
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>
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），结构如下
+-------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+----------------+
mysql> create database zzd;
Query OK, 1 row affected (0.00 sec)
mysql> use zzd;
Database changed
mysql> create table student(id int not null primary key auto_increment,name varchar(20),age tinyint(2));
Query OK, 0 rows affected (0.00 sec)
mysql> desc student;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| age | tinyint(2) | YES | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 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(name,age) values('tom',20),('jerry',23),('wangqing',25),('sean',28),('zhangshan',26),('zhangshan',20),('lisi',null),('chenshuo',10),('wangwu',3),('qiuyi',15),('qiuxiaotian',20);
Query OK, 11 rows affected (0.00 sec)
Records: 11 Duplicates: 0 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 | 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, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student where name = 'lisi';
+----+------+------+
| id | name | age |
+----+------+------+
| 7 | lisi | 50 |
+----+------+------+
1 row 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 |
+----+-------------+------+
| 10 | qiuyi | 15 |
| 1 | tom | 20 |
| 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 * from student where name = 'zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
+----+-----------+------+
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 * from student where name = 'zhangshan' and age > 20;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
+----+-----------+------+
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 * from student where age between 23 and 30;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
+----+-----------+------+
4 rows in set (0.00 sec)
12.修改wangwu的年龄为100
mysql> update student set age = 100 where name = 'wangqing';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from student where name = 'wangqing';
+----+----------+------+
| id | name | age |
+----+----------+------+
| 3 | wangqing | 100 |
+----+----------+------+
1 row 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> 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)
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 | 100 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 7 | lisi | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
10 rows in set (0.00 sec)
