MYSQL

Posted 2020-12-30

mysql 简介
mysql是一种关系数据库管理系统，关系数据库将数据保存在不同的表中，而不是将所有数据放在一个大仓库内，这样就增加了速度并提高了灵活性。
MySQL所使用的 SQL 语言是用于访问数据库的最常用标准化语言。MySQL 软件采用了双授权政策，分为社区版和商业版，由于其体积小、速度快、总体拥有成本低，尤其是开放源码这一特点，一般中小型网站的开发都选择 MySQL 作为网站数据库。
mysql 安装与配置
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 / deb

// 配置mysql的yum源
[[email protected] ~]# cd /usr/src/
[[email protected] src]# ls
debug  kernels
[[email protected] src]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
[[email protected] src]#  yum -y install mysql57-community-release-el7-10.noarch.rpm
[[email protected] src]# ls /etc/yum.repos.d/
[[email protected] ~]#  yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel
mysql 配置
// 启动mysql
[[email protected] ~]#  systemctl start mysqld
[[email protected] ~]# systemctl status mysqld
● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since 五 2018-08-17 16:35:41 CST; 14s ago
     Docs: man:mysqld(8)
// 确保3306端口已经监听起来
[[email protected] ~]# 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
  [[email protected] ~]# grep "password" /var/log/mysqld.log
2018-08-17T08:35:30.972217Z 1 [Note] A temporary password is generated for [email protected]: CYCIoXn;V1)o
  //此处的临时密码为CYCIoXn;V1)o
    //使用获取到的临时密码登录mysql
   [[email protected] ~]# mysql -uroot -p
Enter password:      // 此处输入密码，可以直接复制粘贴。

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

mysql>         //看到有这样的标识则表示登录成功。
// 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 ‘wangqing123!‘;
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
 [[email protected] ~]#  rpm -qa|grep mysql
mysql-community-common-5.7.23-1.el7.x86_64
mysql-community-libs-compat-5.7.23-1.el7.x86_64
mysql-community-libs-5.7.23-1.el7.x86_64
mysql-community-server-5.7.23-1.el7.x86_64
mysql-community-devel-5.7.23-1.el7.x86_64
mysql57-community-release-el7-10.noarch
mysql-community-client-5.7.23-1.el7.x86_64
[[email protected] ~]# yum -y remove mysql57-community-release-el7-10.noarch

mysql 的程序组成
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
服务器
mysqld
mysql 工具使用
// 语法：mysql [ OPTINS] [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
-pPAS1SWORD // 指定用户的密码
-P# //指定数据库监听的端口
-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

[[email protected] ~]# mysql -uroot -pwangqing123! -h127.0.0.1

// 注意，不推荐直接在命令行里直接用。
[[email protected] ~]# mysql -uroot -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or g.
服务器监听的两种socket地址
socket 类型
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）
server 地址只能是：localhost , 127.0.0.1

DDL 操作

数据库操作
创建数据库wangqingge
mysql> CREATE DATABASE IF NOT EXISTS wangqingge;
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 |
| wangqingge |
+--------------------+
5 rows in set (0.07 sec)

//删除数据库wangqingge
mysql> DROP DATABASE IF EXISTS wangqingge;
Query OK, 0 rows affected (0.08 sec)

mysql> SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.01 sec)

表操作
在数据库wangqingge里创建表wangqing
mysql> CREATE DATABASE wangqingge; //创建数据库wangqingge
Query OK, 1 row affected (0.00 sec)

mysql> use wangqingge; //进入wangqingge数据库
Database changed

mysql> CREATE TABLE wangqing (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint); //创建wangqing表
Query OK, 0 rows affected (0.07 sec)

查看当前数据库有哪些表
mysql> SHOW TABLES;
+----------------------+
| Tables_in_wangqingge |
+----------------------+
| wangqing |
+----------------------+
1 row in set (0.00 sec)

删除表wangqing
mysql> DROP TABLE wangqing;
Query OK, 0 rows affected (0.01 sec)

查看某表的状态
//语法：SHOW TABLE STATUS LIKE ‘table_name‘G

DML操作

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

作业练习

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
[[email protected] ~]#  mysql -uroot -p -h127.0.0.1
mysql> CREATE DATABASE yanyinglai;
Query OK, 1 row affected (0.00 sec)   创建数据库
mysql> SHOW databases;    查看当前数据库
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| yanyinglai         |
+--------------------+
5 rows in set (0.00 sec)

mysql> use yanyinglai;   进入yabyinglai数据库
Database changed

mysql> CREATE TABLE student (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint);
Query OK, 0 rows affected (0.02 sec)  创建表

mysql> SHOW TABLES;
+----------------------+
| Tables_in_yanyinglai |
+----------------------+
| student              |
+----------------------+
1 row in set (0.00 sec)   查看表

mysql> DESC yanyinglai.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 (0.06 sec)

查看下该新建的表有无内容（用select语句）

查看表信息mysql> select * from student;

往新建的student表中插入数据（用insert语句），结果应如下
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 |

向表中插入数据mysql> insert into student (id,name,age) values (1,‘tom‘,20),(2,‘jerry‘,23),(3,‘hejiee‘,25),(4,‘sean‘,28),(5,‘zhangshan‘,26),(6,‘zhangshan‘,20),(7,‘lisi‘,NULL),(8,‘ran‘,10),(9,‘wangwu‘,3),(10,‘qiuyi‘,15),(11,‘wangbadan‘,20);

修改lisi的年龄为50

mysql> update student set age=50 where name = ‘lisi‘;

以sge字段降序排序

mysql> select * from student order by age desc;

查询student表中年龄最小的3位同学

mysql> select * from student order by age limit 3;

查询student表中年龄最大的4位同学

mysql> select * from student order by age desc limit 4;

查询student表中名字叫zhangshan的记录
mysql> select * from student where name=‘zhangshan‘;

查询student表中名字叫zhangsan且年龄大于20的记录

mysql> select * from student where name=‘zhangshan‘ and age>20;

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;

修改wangwu的年龄为100

mysql> update student set age=100 where name=‘wangwu‘;

删除student中名字叫zhangsan且年龄小于等于20的记录

mysql> delete from student where name=‘zhangshan‘ and age<=20;