mysql基础
1. 关系型数据库介绍
1.1 数据结构模型
数据结构模型主要有：
- 层次模型
- 网状结构
- 关系模型
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
事务： 多个操作被当作一个整体对待就称为一个事务
要看一个关系型数据库是否支持事务，需要看其是否支持并满足ACID测试
ACID：ACID是事务的一个基本标准
- A：Automicity，原子性
- C：Consistency，一致性
- I：Isolation，隔离性
- D：Durability，持久性
SQL： StructureQueryLanguage，结构化查询语言
约束： constraint，向数据表提供的数据要遵守的限制
- 主键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。且必须提供数据，不能为空（NOT NULL）。
一个表只能存在一个
-
惟一键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。允许为空（NULL）
一个表可以存在多个
外键约束：一个表中的某字段可填入数据取决于另一个表的主键已有的数据
检查性约束
索引： 将表中的一个或多个字段中的数据复制一份另存，并且这些数据需要按特定次序排序存储
关系运算：
- 选择：挑选出符合条件的行（部分行）
- 投影：挑选出需要的字段
- 连接
数据抽象方式：
- 物理层：决定数据的存储格式，即RDBMS在磁盘上如何组织文件
- 逻辑层：描述DB存储什么数据，以及数据间存在什么样的关系
- 视图层：描述DB中的部分数据
1.3 关系型数据库的常见组件
关系型数据库的常见组件有：
- 数据库：database
- 表：table，由行（row）和列（column）组成
- 索引：index
- 视图：view
- 用户：user
- 权限：privilege
- 存储过程：procedure
- 存储函数：function
- 触发器：trigger
- 事件调度器：event scheduler
1.4 SQL语句
SQL语句有三种类型：
- DDL：DataDefinationLanguage，数据定义语言
- DML:DataManipulationLanguage，数据操纵语言
- DCL：DataControlLanguage，数据控制语言
| SQL语句类型 | 对应操作 |
|---|---|
| DDL | CREATE：创建 DROP：删除 ALTER：修改 |
| DML | INSERT：向表中插入数据 DELETE：删除表中数据 UPDATE：更新表中数据 SELECT：查询表中数据 |
| DCL | GRANT：授权 REVOKE：移除授权 |
2. mysql安装与配置
2.1 mysql安装
mysql安装方式有三种：
- 源代码：编译安装
- 二进制格式的程序包：展开至特定路径，并经过简单配置后即可使用
- 程序包管理器管理的程序包：
- rpm：有两种
- OS Vendor：操作系统发行商提供的
- 项目官方提供的
- rpm：有两种
- deb
//配置mysql的yum源
[root@localhost ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
下载过程略
[root@localhost ~]# ls
debug kernels mysql57-community-release-el7-10.noarch.rpm
[root@localhost ~]# yum -y install mysql57-community-release-el7-10.noarch.rpm
Loaded plugins: fastestmirror, product-id, search-disabled-repos, subscription-
: manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
Examining mysql57-community-release-el7-10.noarch.rpm: mysql57-community-release-el7-10.noarch
....
Installed:
mysql57-community-release.noarch 0:el7-10
Complete!
[root@localhost ~]# ls /etc/yum.repos.d/
mysql-community.repo mysql-community-source.repo
//安装mysql5.7
[root@localhost ~]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel
Loaded plugins: fastestmirror, product-id, search-disabled-repos, subscription-
: manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package mysql-community-client.x86_64 0:5.7.23-1.el7 will be installed
--> Processing Dependency: mysql-community-libs(x86-64) >= 5.7.9 for package: mysql-community-client-5.7.23-1.el7.x86_64
....
Installed:
mysql-community-client.x86_64 0:5.7.23-1.el7
mysql-community-common.x86_64 0:5.7.23-1.el7
mysql-community-devel.x86_64 0:5.7.23-1.el7
mysql-community-libs.x86_64 0:5.7.23-1.el7
mysql-community-libs-compat.x86_64 0:5.7.23-1.el7
mysql-community-server.x86_64 0:5.7.23-1.el7
Replaced:
mariadb-libs.x86_64 1:5.5.56-2.el7
Complete!
2.2 mysql配置
root@ly ~]# systemctl start mysqld
[root@ly ~]# systemctl status mysqld
● mysqld.service - MySQL Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: active (running) since 二 2019-04-23 00:55:37 CST; 30s ago
Docs: man:mysqld(8)
http://dev.mysql.com/doc/refman/en/using-systemd.html
Process: 3071 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
Process: 2998 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
Main PID: 3075 (mysqld)
CGroup: /system.slice/mysqld.service
└─3075 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
4月 23 00:55:34 ly systemd[1]: Starting MySQL Server...
4月 23 00:55:37 ly systemd[1]: Started MySQL Server.
[root@ly ~]#
//确保3306端口已经监听起来
[root@ly ~]# ss -antl
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:22 *:*
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 128 :::22 :::*
LISTEN 0 100 ::1:25 :::*
LISTEN 0 80 :::3306 :::*
//在日志文件中找出临时密码
[root@ly ~]# grep "password" /var/log/mysqld.log
2019-04-22T16:55:35.202199Z 1 [Note] A temporary password is generated for root@localhost: :i3mgfp7Nlz.
//此处的临时密码为:i3mgfp7Nlz.
//使用获取到的临时密码登录mysql
[root@ly ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.25
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
//看到有这样的标识符则表示成功登录了
//修改mysql登录密码
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'ly123';
Query OK, 0 rows affected (0.00 sec)
mysql> quit
Bye
//为避免mysql自动升级，这里需要卸载最开始安装的yum源
[root@ly ~]# rpm -qa|grep mysql
mysql57-community-release-el7-10.noarch
mysql-community-client-5.7.25-1.el7.x86_64
mysql-community-devel-5.7.25-1.el7.x86_64
mysql-community-libs-5.7.25-1.el7.x86_64
mysql-community-libs-compat-5.7.25-1.el7.x86_64
mysql-community-server-5.7.25-1.el7.x86_64
mysql-community-common-5.7.25-1.el7.x86_64
[root@ly ~]# yum -y remove mysql57-community-release-el7-10.noarch
已加载插件：product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
Repository base is listed more than once in the configuration
Repository updates is listed more than once in the configuration
Repository extras is listed more than once in the configuration
Repository centosplus is listed more than once in the configuration
正在解决依赖关系
--> 正在检查事务
---> 软件包 mysql57-community-release.noarch.0.el7-10 将被 删除
--> 解决依赖关系完成
依赖关系解决
.....
删除:
mysql57-community-release.noarch 0:el7-10
完毕！
3. mysql的程序组成
- 客户端
- mysql：CLI交互式客户端程序
- mysql_secure_installation：安全初始化，强烈建议安装完以后执行此命令
- mysqldump：mysql备份工具
- mysqladmin
- 服务器端
- mysqld
3.1 mysql工具使用
//语法：mysql [OPTIONS] [database]
//常用的OPTIONS：
-uUSERNAME //指定用户名，默认为root
-hHOST //指定服务器主机，默认为localhost，推荐使用ip地址
-pPASSWORD //指定用户的密码
-P# //指定数据库监听的端口，这里的#需用实际的端口号代替，如-P3307
-V //查看当前使用的mysql版本
-e //不登录mysql执行sql语句后退出，常用于脚本
[root@ly ~]# mysql -V
mysql Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using EditLine wrapper
[root@ly ~]# mysql -uroot -ply123 -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 3
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
//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@ly ~]# mysql -uroot -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
[root@ly ~]# mysql -uroot -p -h 127.0.0.1 -e 'SHOW DATABASES;'
Enter password:
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
3.2 服务器监听的两种socket地址
| socket类型 | 说明 |
|---|---|
| ip socket | 默认监听在tcp的3306端口，支持远程通信 |
| unix sock | 监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock）仅支持本地通信 server地址只能是：localhost，127.0.0.1 |
4. mysql数据库操作
4.1 DDL操作
4.1.1 数据库操作
//创建数据库
//语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME';
//创建数据库liuyi
mysql> CREATE DATABASE IF NOT EXISTS liuyi;
Query OK, 1 row affected (0.00 sec)
mysql>
//查看当前实例有哪些数据库
mysql> show databases;(可大写亦可小写)
+--------------------+
| Database |
+--------------------+
| information_schema |
| liuyi |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql>
//删除数据库
//语法：DROP DATABASE [IF EXISTS] 'DB_NAME';
//删除数据库liuyi
mysql> drop database if exists liuyi;
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)
mysql>
4.1.2 表操作
//创建表
//语法：CREATE TABLE table_name (col1 datatype 修饰符,col2 datatype 修饰符) ENGINE='存储引擎类型';
//在数据库liuyi里创建表liucongrong
mysql> CREATE DATABASE IF NOT EXISTS liuyi;
Query OK, 1 row affected (0.00 sec) ////创建数据库liuyi
mysql> use liuyi;
Database changed //进入liuyi数据库
mysql>
mysql> CREATE TABLE liucongrong (id int NOT NULL,name VARCHAR(100) NOT NULL,aage tinyint);
Query OK, 0 rows affected (0.01 sec) //创建liucongrong表
//查看当前数据库有哪些表
mysql> show tables;
+-----------------+
| Tables_in_liuyi |
+-----------------+
| liucongrong |
+-----------------+
1 row in set (0.00 sec)
mysql>
//删除表
//语法：DROP TABLE [ IF EXISTS ] 'table_name';
//删除表liucongrong
mysql> drop table liucongrong;
Query OK, 0 rows affected (0.00 sec)
mysql> show tables;
Empty set (0.01 sec)
4.1.3 用户操作
mysql用户帐号由两部分组成，如'USERNAME'@'HOST'，表示此USERNAME只能从此HOST上远程登录
这里（'USERNAME'@'HOST'）的HOST用于限制此用户可通过哪些主机远程连接mysql程序，其值可为：
- IP地址，如：192.168.153.151
- 通配符
- %：匹配任意长度的任意字符，常用于设置允许从任何主机登录
- _：匹配任意单个字符
//数据库用户创建
//语法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password'];
//创建数据库用户liucongrong
mysql> CREATE USER 'liucongrong'@'127.0.0.1' IDENTIFIED BY 'ly123';
Query OK, 0 rows affected (0.00 sec)
//使用新创建的用户和密码登录
[root@ly ~]# mysql -uliucongrong -ply123 -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 9
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
//删除数据库用户
//语法：DROP USER 'username'@'host';
[root@ly ~]# mysql -uroot -ply123 -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: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> drop user liucongrong;
ERROR 1396 (HY000): Operation DROP USER failed for 'liucongrong'@'%'
mysql> drop user liucongrong@127.0.0.1;
Query OK, 0 rows affected (0.00 sec)
mysql>
4.1.4 查看命令SHOW
mysql> SHOW CHARACTER SET; //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)
mysql>
mysql> SHOW ENGINES; //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)
mysql> SHOW DATABASES; //查看数据库信息
mysql> SHOW DATABASES;
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| liuyi |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> SHOW TABLES FROM wangqingge; //不进入某数据库而列出其包含的所有表
mysql> SHOW TABLES FROM wangqingge;
+----------------------+
| Tables_in_liuyi |
+----------------------+
| liuyi |
+----------------------+
1 row in set (0.00 sec)
//查看表结构
//语法：DESC [db_name.]table_name;
mysql> DESC liuyi.liucongrong;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.02 sec)
//查看某表的创建命令
//语法：SHOW CREATE TABLE table_name;
mysql> SHOW CREATE TABLE liuyi.liucongrong;
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------+
| liucongrong | CREATE TABLE `liucongrong` (
`id` int(11) NOT NULL,
`name` varchar(100) NOT NULL,
`age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
//查看某表的状态
//语法：SHOW TABLE STATUS LIKE 'table_name'\G
mysql> use liuyi;
//查看liuyi表的状态
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> SHOW TABLE STATUS LIKE 'liucongrong'\G //查看liucongrong表的状态
*************************** 1. row ***************************
Name: liucongrong
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: 2019-04-23 03:40:04
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
4.1.5 获取帮助
//获取命令使用帮助
//语法：HELP keyword;
mysql> HELP CREATE TABLE; //获取创建表的帮助
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
[table_options]
[partition_options]
[IGNORE | REPLACE]
[AS] query_expression
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
{ LIKE old_tbl_name | (LIKE old_tbl_name) }
create_definition:
col_name column_definition
| [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (key_part,...)
[index_option] ...
| {INDEX|KEY} [index_name] [index_type] (key_part,...)
[index_option] ...
| [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY]
[index_name] [index_type] (key_part,...)
[index_option] ...
| {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (key_part,...)
[index_option] ...
| [CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (col_name,...) reference_definition
| CHECK (expr)
column_definition:
data_type [NOT NULL | NULL] [DEFAULT default_value]
[AUTO_INCREMENT] [UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
[COLLATE collation_name]
[COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
[STORAGE {DISK|MEMORY|DEFAULT}]
[reference_definition]
| data_type [GENERATED ALWAYS] AS (expression)
[VIRTUAL | STORED] [NOT NULL | NULL]
[UNIQUE [KEY]] [[PRIMARY] KEY]
[COMMENT 'string']
data_type:
(see http://dev.mysql.com/doc/refman/5.7/en/data-types.html)
key_part:
col_name [(length)] [ASC | DESC]
index_type:
USING {BTREE | HASH}
index_option:
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string
......
4.2 DML操作
DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。
4.2.1 INSERT语句
//DML操作之增操作insert
//语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...
mysql> use liucongrong;
Database changed
mysql> create table student (id int not null,name varchar(100) not null,age tinyint(4) null);
Query OK, 0 rows affected (0.01 sec)
mysql> desc student;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> select * from student;
Empty set (0.00 sec)
mysql> insert into student value (1,'tom',20);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO wangqing (id,name,age) VALUES (2,'jerry',23),(3,'wangqing',25),(4,'sean',28),(5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',NULL); //一次插入多条记录
Query OK, 4 rows affected (0.01 sec)
Records: 4 Duplicates: 0 Warnings: 0
4.2.2 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，如col1 AS alias1 当表名很长时用别名代替 |
条件判断语句WHERE
| 操作类型 | 常用操作符 |
|---|---|
| 操作符 | >，<，>=，<=，=，!= BETWEEN column# AND column# LIKE：模糊匹配 RLIKE：基于正则表达式进行模式匹配 IS NOT NULL：非空 IS NULL：空 |
| 条件逻辑操作 | AND OR NOT |
ORDER BY：排序，默认为升序（ASC）
| ORDER BY语句 | 意义 |
|---|---|
| ORDER BY ‘column_name' | 根据column_name进行升序排序 |
| ORDER BY 'column_name' DESC | 根据column_name进行降序排序 |
| ORDER BY ’column_name' LIMIT 2 | 根据column_name进行升序排序并只取前2个结果 |
| ORDER BY ‘column_name' LIMIT 1,2 | 根据column_name进行升序排序并且略过第1个结果取后面的2个结果 |
//DML操作之查操作select
//语法：SELECT column1,column2,... FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
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> select name from student;
+-------------+
| name |
+-------------+
| tom |
| jerry |
| wangqing |
| sean |
| zhangshan |
| lisi |
| chenshuo |
| wangwu |
| qiuyi |
| qiuxiaotian |
+-------------+
10 rows in set (0.01 sec)
mysql> select * from student order by age;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 6 | zhangshan | 20 |
| 7 | lisi | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
11 rows in set (0.00 sec)
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)
mysql> select * from student order by age limit 3;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 9 | wangwu | 3 |
| 8 | chenshuo | 10 |
| 10 | qiuyi | 15 |
+----+----------+------+
3 rows in set (0.00 sec)
mysql> select * from student where age >=20;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 7 | lisi | 50 |
| 9 | wangwu | 100 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
8 rows in set (0.00 sec)
mysql> select * from student where age >20 and name = 'zhangshan';
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 5 | zhangshan | 26 |
+----+-----------+------+
1 row in set (0.00 sec)
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)
mysql> select * from student where age is not null;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 7 | lisi | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 100 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
10 rows in set (0.00 sec)
mysql> select * from student where age is null;
Empty set (0.00 sec)
4.2.3 update语句
//DML操作之改操作update
//语法：UPDATE table_name SET column1 = new_value1[,column2 = new_value2,...] [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
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> update student set age = 50 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 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 | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 3 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
11 rows in set (0.00 sec)
4.2.4 delete语句
//DML操作之删操作delete
//语法：DELETE FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
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 | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 100 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
11 rows in set (0.00 sec)
mysql> delete from student where id = 6;
Query OK, 1 row affected (0.00 sec)
mysql> select * from student;
+----+-------------+------+
| id | name | age |
+----+-------------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
| 4 | sean | 28 |
| 5 | zhangshan | 26 |
| 7 | lisi | 50 |
| 8 | chenshuo | 10 |
| 9 | wangwu | 100 |
| 10 | qiuyi | 15 |
| 11 | qiuxiaotian | 20 |
+----+-------------+------+
10 rows in set (0.00 sec)
mysql> delete from student;
Query OK, 10 rows affected (0.00 sec) //删除整张表的内容
mysql> desc student;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
4.2.5 truncate语句
truncate与delete的区别：
| 语句类型 | 特点 |
|---|---|
| delete | DELETE删除表内容时仅删除内容，但会保留表结构 DELETE语句每次删除一行，并在事务日志中为所删除的每行记录一项 可以通过回滚事务日志恢复数据 非常占用空间 |
| truncate | 删除表中所有数据，且无法恢复 表结构、约束和索引等保持不变，新添加的行计数值重置为初始值 执行速度比DELETE快，且使用的系统和事务日志资源少 通过释放存储表数据所用的数据页来删除数据，并且只在事务日志中记录页的释放 对于有外键约束引用的表，不能使用TRUNCATE TABLE删除数据 不能用于加入了索引视图的表 |
//语法：TRUNCATE table_name;
mysql> select * from student;
+----+----------+------+
| id | name | age |
+----+----------+------+
| 1 | tom | 20 |
| 2 | jerry | 23 |
| 3 | wangqing | 25 |
+----+----------+------+
3 rows in set (0.00 sec)
mysql> truncate student;
Query OK, 0 rows affected (0.01 sec)
mysql> select * from student;
Empty set (0.00 sec)
mysql> desc student;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
4.3 DCL操作
4.3.1 创建授权grant
权限类型(priv_type)
| 权限类型 | 代表什么？ |
|---|---|
| ALL | 所有权限 |
| SELECT | 读取内容的权限 |
| INSERT | 插入内容的权限 |
| UPDATE | 更新内容的权限 |
| DELETE | 删除内容的权限 |
指定要操作的对象db_name.table_name
| 表示方式 | 意义 |
|---|---|
| * . * | 所有库的所有表 |
| db_name | 指定库的所有表 |
| db_name.table_name | 指定库的指定表 |
WITH GRANT OPTION：被授权的用户可将自己的权限副本转赠给其他用户，说白点就是将自己的权限完全复制给另一个用户。不建议使用。
GRANT priv_type,... ON [object_type] db_name.table_name TO ‘username'@'host' [IDENTIFIED BY 'password'] [WITH GRANT OPTION];
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| liucongrong |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
//授权wangqing用户在数据库本机上登录访问所有数据库
mysql> GRANT ALL ON *.* TO 'wangqing'@'localhost' IDENTIFIED BY 'wangqing123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> GRANT ALL ON *.* TO 'liucongrong'@'127.0.0.1' IDENTIFIED BY 'liucongrong123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权liucongrong用户在192.168.153.152上远程登录访问liucongrong数据库
mysql> GRANT ALL ON liucongrong* TO 'liucong'@'192.168.153.152' IDENTIFIED BY 'liucongrong123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)
//授权liucongrong用户在所有位置上远程登录访问liucongrong数据库
mysql> GRANT ALL ON *.* TO 'liucongrong'@'%' IDENTIFIED BY 'liucongrong123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)
4.3.2 查看授权
//查看当前登录用户的授权信息
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
//查看指定用户wangqing的授权信息
mysql> SHOW GRANTS FOR liucongrong;
+-----------------------------------------------+
| Grants for liucongrong@% |
+-----------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'liucongrong'@'%' |
+-----------------------------------------------+
1 row in set (0.00 sec)
mysql> SHOW GRANTS FOR 'liucongrong'@'localhost';
+-------------------------------------------------------+
| Grants for liucongrong@localhost |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'liucongrong'@'localhost' |
+-------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SHOW GRANTS FOR 'liucongrong'@'127.0.0.1';
+-------------------------------------------------------+
| Grants for liucongrong@127.0.0.1 |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'liucongrong'@'127.0.0.1' |
+-------------------------------------------------------+
1 row in set (0.00 sec)
4.3.3 取消授权REVOKE
//语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';
mysql> REVOKE ALL ON *.* FROM 'liucongrong'@'192.168.153.152';
Query OK, 0 rows affected (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (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;