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)
