MySQL数据库基础进阶

原创已于 2022-07-27 21:58:40 修改 · 521 阅读

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于 2022-07-26 10:57:14 首次发布

关系型数据库介绍

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(行)，column(列)
数据库管理系统：DBMS
关系：Relational，RDBMS

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

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

SQL语句

SQL语句有三种类型：

DDL：Data Defination Language，数据定义语言
DML：Data Manipulation Language，数据操纵语言
DCL：Data Control Language，数据控制语言

SQL语句类型	对应操作
DDL	CREATE：创建 DROP：删除 ALTER：修改
DML	INSERT：向表中插入数据 DELETE：删除表中数据 UPDATE：更新表中数据 SELECT：查询表中数据
DCL	GRANT：授权 REVOKE：移除授权

mysql安装与配置

mysql安装

mysql安装方式有三种：

源代码：编译安装
二进制格式的程序包：展开至特定路径，并经过简单配置后即可使用
程序包管理器管理的程序包：
- rpm：有两种
  - OS Vendor：操作系统发行商提供的
  - 项目官方提供的
- deb

配置mysql的yum源

[root@localhost ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm

位置：https://repo.mysql.com//mysql57-community-release-el7-11.noarch.rpm [跟随至新的 URL]
--2022-07-22 05:48:05--  https://repo.mysql.com//mysql57-community-release-el7-11.noarch.rpm
正在解析主机 repo.mysql.com (repo.mysql.com)... 23.55.248.248
正在连接 repo.mysql.com (repo.mysql.com)|23.55.248.248|:443... 已连接。
已发出 HTTP 请求，正在等待回应... 200 OK
长度：25680 (25K) [application/x-redhat-package-manager]
正在保存至: “mysql57-community-release-el7-11.noarch.rpm”

mysql57-community-release-el7-11.noarch.rpm    100%[=================================================================================================>]  25.08K  83.1KB/s  用时 0.3s

2022-07-22 05:48:07 (83.1 KB/s) - 已保存 “mysql57-community-release-el7-11.noarch.rpm” [25680/25680])

[root@localhost ~]#

[root@localhost ~]# rpm -Uvh mysql57-community-release-el7-11.noarch.rpm
警告：mysql57-community-release-el7-11.noarch.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
Verifying...                          ################################# [100%]
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql57-community-release-el7-11 ################################# [100%]

使用yum安装mysql5.7,关闭此模块yum module disable mysql

[root@localhost ~]# yum module disable mysql
上次元数据过期检查：0:13:35 前，执行于 2022年07月22日 星期五 06时04分16秒。
依赖关系解决。
=========================================================================================================================================================================================
 软件包                                      架构                                       版本                                           仓库                                         大小
=========================================================================================================================================================================================
禁用模块:
 mysql

事务概要
=========================================================================================================================================================================================

确定吗？[y/N]： y
完毕！
[root@localhost ~]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel --nogpgcheck
....

已安装:
  mysql-community-client-5.7.38-1.el7.x86_64    mysql-community-common-5.7.38-1.el7.x86_64       mysql-community-devel-5.7.38-1.el7.x86_64    mysql-community-libs-5.7.38-1.el7.x86_64
  mysql-community-server-5.7.38-1.el7.x86_64    ncurses-compat-libs-6.1-9.20180224.el8.x86_64

完毕！
[root@localhost ~]#

mysql配置

启动服务并设置开机自启

[root@localhost ~]# systemctl enable --now mysqld
[root@localhost ~]# systemctl status mysqld
● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2022-07-22 06:22:19 EDT; 2s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 3856 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
  Process: 3802 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 3858 (mysqld)
    Tasks: 27 (limit: 23330)
   Memory: 328.2M
   CGroup: /system.slice/mysqld.service
           └─3858 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid

7月 22 06:22:15 localhost.localdomain systemd[1]: Starting MySQL Server...
7月 22 06:22:19 localhost.localdomain systemd[1]: Started MySQL Server.
[root@localhost ~]#

查看端口

[root@localhost ~]# ss -antlp
State          Recv-Q         Send-Q                  Local Address:Port                   Peer Address:Port         Process
LISTEN         0              128                         127.0.0.1:6010                        0.0.0.0:*             users:(("sshd",pid=2427,fd=15))
LISTEN         0              128                           0.0.0.0:111                         0.0.0.0:*             users:(("rpcbind",pid=1016,fd=4),("systemd",pid=1,fd=116))
LISTEN         0              32                      192.168.122.1:53                          0.0.0.0:*             users:(("dnsmasq",pid=2125,fd=6))
LISTEN         0              128                           0.0.0.0:22                          0.0.0.0:*             users:(("sshd",pid=1279,fd=5))
LISTEN         0              5                           127.0.0.1:631                         0.0.0.0:*             users:(("cupsd",pid=1285,fd=10))
LISTEN         0              128                             [::1]:6010                           [::]:*             users:(("sshd",pid=2427,fd=14))
LISTEN         0              80                                  *:3306                              *:*             users:(("mysqld",pid=3858,fd=22))
LISTEN         0              128                              [::]:111                            [::]:*             users:(("rpcbind",pid=1016,fd=6),("systemd",pid=1,fd=118))
LISTEN         0              128                              [::]:22                             [::]:*             users:(("sshd",pid=1279,fd=7))
LISTEN         0              5                               [::1]:631                            [::]:*             users:(("cupsd",pid=1285,fd=9))
[root@localhost ~]#

查看密码

[root@localhost ~]# grep "password" /var/log/mysqld.log
2022-07-22T10:22:17.900718Z 1 [Note] A temporary password is generated for root@localhost: bf.Zx4-qShsi

登录并修改密码

[root@localhost ~]# mysql -uroot -pbf.Zx4-qShsi
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 2
Server version: 5.7.38

Copyright (c) 2000, 2022, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'haha123';
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye
[root@localhost ~]#

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

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@localhost ~]# mysql -V
mysql  Ver 14.14 Distrib 5.7.23, for Linux (x86_64) using  EditLine wrapper

[root@localhost ~]# mysql -uroot -phaha123! -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 4
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, 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@localhost ~]# mysql -uroot -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, 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@localhost ~]# mysql -uroot -p -h 127.0.0.1 -e 'SHOW DATABASES;'
Enter password:
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| hahha        |
+--------------------+

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

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
在这里插入图片描述

在这里插入图片描述

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

CHAR 和 VARCHAR 类型类似，但它们保存和检索的方式不同。它们的最大长度和是否尾部空格被保留等方面也不同。在存储或检索过程中不进行大小写转换。

BINARY 和 VARBINARY 类似于 CHAR 和 VARCHAR，不同的是它们包含二进制字符串而不要非二进制字符串。也就是说，它们包含字节字符串而不是字符字符串。这说明它们没有字符集，并且排序和比较基于列值字节的数值值。

BLOB 是一个二进制大对象，可以容纳可变数量的数据。有 4 种 BLOB 类型：TINYBLOB、BLOB、MEDIUMBLOB 和 LONGBLOB。它们区别在于可容纳存储范围不同。

有 4 种 TEXT 类型：TINYTEXT、TEXT、MEDIUMTEXT 和 LONGTEXT。对应的这 4 种 BLOB 类型，可存储的最大长度不同，可根据实际情况选择。

mysql数据库操作

DDL操作

数据库操作

创建数据库

语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME';
创建数据库haha
mysql> CREATE DATABASE IF NOT EXISTS haha;
Query OK, 1 row affected (0.00 sec)

查看当前实例有哪些数据库

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| haha        |
+--------------------+
5 rows in set (0.00 sec)

删除数据库
语法：DROP DATABASE [IF EXISTS] ‘DB_NAME’;
删除数据库haha

mysql> DROP DATABASE IF EXISTS haha;
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)

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haha里创建表haha

mysql> CREATE DATABASE haha;      //创建数据库haha
Query OK, 1 row affected (0.00 sec)

mysql> use haha;      //进入haha数据库
Database changed
mysql> CREATE TABLE haha (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint);      //创建haha表
Query OK, 0 rows affected (0.09 sec)

查看当前数据库有哪些表

mysql> SHOW TABLES;
+----------------------+
| Tables_in_wangqingge |
+----------------------+
| haha                 |
+----------------------+
1 row in set (0.00 sec)

删除表
语法：DROP TABLE [ IF EXISTS ] ‘table_name’;
删除表haha

mysql> DROP TABLE haha;
Query OK, 0 rows affected (0.01 sec)

mysql> SHOW TABLES;
Empty set (0.00 sec)

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

数据库用户创建

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

mysql> CREATE USER 'hehe'@'127.0.0.1' IDENTIFIED BY 'hehe123!';
Query OK, 0 rows affected (0.00 sec)

使用新创建的用户和密码登录

[root@localhost ~]# mysql -uhehe -phehe123! -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, 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'; 
mysql> DROP USER 'hehe'@'127.0.0.1';
Query OK, 0 rows affected (0.00 sec)

查看命令SHOW

mysql> SHOW CHARACTER SET;      //查看支持的所有字符集
+----------+---------------------------------+---------------------+--------+
| 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 | 
......
......

mysql> SHOW ENGINES;        //查看当前数据库支持的所有存储引擎
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| 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
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| hehe               |
+--------------------+
5 rows in set (0.00 sec)

mysql> SHOW TABLES FROM hehe;         //不进入某数据库而列出其包含的所有表
+----------------------+
| Tables_in_wangqingge |
+----------------------+
| hehe                 |
+----------------------+
1 row in set (0.00 sec)

查看表结构

语法：DESC [db_name.]table_name;
mysql> DESC hehe.haha;   //数据库名.表名
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.03 sec)

查看某表的创建命令

语法：SHOW CREATE TABLE table_name;
mysql> SHOW CREATE TABLE hehe.haha;
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                              |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
| wangqing | CREATE TABLE `haha` (
  `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 hehe;      //进入数据库hehe
Database changed
mysql> SHOW TABLE STATUS LIKE 'haha'\G      //查看haha表的状态
*************************** 1. row ***************************
           Name: haha
         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 18:53:21
    Update_time: NULL
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.00 sec)

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
 ......
 ......

DML操作

DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。

INSERT语句

DML操作之增操作insert

语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...

mysql> usehehe;
Database changed
mysql> INSERT INTO haha (id,name,age) VALUE (1,'tom',20);       //一次插入一条记录
Query OK, 1 row affected (0.01 sec)


mysql> INSERT INTO haha (id,name,age) VALUES (2,'jerry',23),(3,'hgaf',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

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> use hehe;
Database changed
mysql> select * from haha;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jdddb     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT name FROM haha;
+-----------+
| name      |
+-----------+
| tom       |
| jerry     |
| jdddb     |
| sean      |
| zhangshan |
| zhangshan |
| lisi      |
+-----------+
7 rows in set (0.01 sec)

mysql> SELECT * FROM haha ORDER BY age;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      | NULL |
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
|  2 | jerry     |   23 |
|  3 | jdddb     |   25 |
|  5 | zhangshan |   26 |
|  4 | sean      |   28 |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT * FROM haha ORDER BY age DESC;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  3 | jdddb     |   25 |
|  2 | jerry     |   23 |
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> SELECT * FROM haha ORDER BY age limit 2;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
|  1 | tom  |   20 |
+----+------+------+
2 rows in set (0.00 sec)

mysql> SELECT * FROM haha ORDER BY age limit 1,2;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  6 | zhangshan |   20 |
+----+-----------+------+
2 rows in set (0.00 sec)


mysql> SELECT * FROM haha WHERE age >= 25;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  3 | jdddb     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
3 rows in set (0.00 sec)

mysql> SELECT * FROM haha WHERE age >= 25 AND name = 'zhangshan';
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | zhangshan |   26 |
+----+-----------+------+
1 row in set (0.00 sec)

mysql> SELECT * FROM haha WHERE age BETWEEN 23 and 28;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  2 | jerry     |   23 |
|  3 | jdddb     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
4 rows in set (0.00 sec)

mysql> select * from haha where age is not null;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jdddb     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
+----+-----------+------+
6 rows in set (0.00 sec)

mysql> select * from haha where age is null;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
+----+------+------+
1 row in set (0.00 sec)

date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 haha;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jfadd     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> update haha set age = 30 where name = 'lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from haha where name = 'lisi';
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi |   30 |
+----+------+------+
1 row in set (0.00 sec)

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 haha;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jcdd      |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      |   30 |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> delete from haha where id = 7;       //删除某条记录
Query OK, 1 row affected (0.00 sec)

mysql> select * from haha;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jahdd     |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
+----+-----------+------+
6 rows in set (0.00 sec)


mysql> delete from haha;        //删除整张表的内容
Query OK, 6 rows affected (0.00 sec)

mysql> select * from haha;
Empty set (0.00 sec)

mysql> desc haha;
+-------+--------------+------+-----+---------+-------+
| 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)

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 haha;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | jdddb   |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
|  7 | lisi      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> truncate haha;
Query OK, 0 rows affected (0.01 sec)

mysql> select * from haha;
Empty set (0.00 sec)

mysql> desc haha;
+-------+--------------+------+-----+---------+-------+
| 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)

DCL操作

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 |
| mysql              |
| performance_schema |
| sys                |
| hehe             |
+--------------------+
5 rows in set (0.00 sec)

授权haha用户在数据库本机上登录访问所有数据库

mysql> GRANT ALL ON *.* TO 'haha'@'localhost' IDENTIFIED BY 'haha123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> GRANT ALL ON *.* TO 'haha'@'127.0.0.1' IDENTIFIED BY 'haha123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

授权haha用户在192.168.40.99上远程登录访问hehe数据库

mysql> GRANT ALL ON hehe.* TO 'haha'@'192.168.40.99' IDENTIFIED BY 'haha123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

授权haha用户在所有位置上远程登录访问hehe数据库

mysql> GRANT ALL ON *.* TO 'haha'@'%' IDENTIFIED BY 'haha123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

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haha的授权信息

mysql> SHOW GRANTS FOR haha;
+-----------------------------------------------+
| Grants for haha@%                         |
+-----------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'haha'@'%' |
+-----------------------------------------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'haha'@'localhost';
+-------------------------------------------------------+
| Grants for haha@localhost                         |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'haha'@'localhost' |
+-------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'haha'@'127.0.0.1';
+-------------------------------------------------------+
| Grants for haha@127.0.0.1                         |
+-------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'haha'@'127.0.0.1' |
+-------------------------------------------------------+
1 row in set (0.00 sec)

取消授权REVOKE

语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';

mysql> REVOKE ALL ON *.* FROM 'haha'@'172.16.12.129';
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;

实战案例

1.搭建mysql服务
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），表结构如下：

mysql> create database haha;
Query OK, 1 row affected (0.00 sec)
mysql> use haha;
Database changed
mysql> create table student(id int(11) not null  primary key auto_increment,name varchar(100) not null,age tinyint(4));
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(100) | NO   |     | NULL    |                |
| age   | tinyint(4)   | YES  |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.03 sec)
mysql>

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)

mysql>

4.往新建的student表中插入数据（用insert语句），结果应如下所示：

mysql> insert student (id,name,age) values (1,'tom',20),(2,'jerry',23),(3,'haha',20),(4,'sean',28),(5,'zhangsan',26),(6,'zhangsan',20),(7,'lisi',NULL),(8,'chenshuo',10),(9,'wangwu',3),(10,'qiuyi',15),(11,'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 | haha        |   20 |
|  4 | sean        |   28 |
|  5 | zhangsan    |   26 |
|  6 | zhangsan    |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)

mysql>

5.修改lisi的年龄为50

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 where name='lisi';
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi |   50 |
+----+------+------+
1 row in set (0.00 sec)

mysql>

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 | zhangsan    |   26 |
|  2 | jerry       |   23 |
|  1 | tom         |   20 |
|  3 | haha        |   20 |
|  6 | zhangsan    |   20 |
| 11 | qiuxiaotian |   20 |
| 10 | qiuyi       |   15 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
+----+-------------+------+
11 rows in set (0.00 sec)

mysql>

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 2,1;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
| 10 | qiuyi       |   15 |
+----+-------------+------+
1 rows in set (0.00 sec)

mysql>

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 | zhangsan |   26 |
|  2 | jerry    |   23 |
+----+----------+------+
4 rows in set (0.00 sec)

mysql>

9.查询student表中名字叫zhangsan的记录

mysql> select * from student where name='zhangsan';
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  5 | zhangsan |   26 |
|  6 | zhangsan |   20 |
+----+----------+------+
2 rows in set (0.00 sec)

mysql>

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='zhangsan' and age > 20;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  5 | zhangsan |   26 |
+----+----------+------+
1 row in set (0.00 sec)

mysql>

11.查询student表中年龄在23到30之间的记录

mysql> select * from student where age BETWEEN 20 and 30;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | haha        |   20 |
|  4 | sean        |   28 |
|  5 | zhangsan    |   26 |
|  6 | zhangsan    |   20 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
7 rows in set (0.00 sec)

mysql>

12.修改wangwu的年龄为100

mysql> update student set  age='100' where name='wangwu';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from student where name='wangwu';
+----+--------+------+
| id | name   | age  |
+----+--------+------+
|  9 | wangwu |  100 |
+----+--------+------+
1 row in set (0.00 sec)

mysql>

13.删除student中名字叫zhangshan且年龄小于等于20的记录

mysql> delete   from student where name='zhangsan' and age<=20;
Query OK, 1 row affected (0.00 sec)

mysql> select * from student where  not name='zhangsan';  //使用not取反查看
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | haha        |   20 |
|  4 | sean        |   28 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
9 rows in set (0.00 sec)

mysql>