mySQL安装与基础配置

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，column

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

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

如果你对ACID感兴趣，可以查看这里了解详细说明，ACID将不作为我们讲解的重点。

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

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
- CREATE：创建
- DROP：删除
- ALTER：修改
DML：Data Manipulation Language，数据操纵语言
- 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：Data Control Language，数据控制语言
- GRANT：授权
- REVOKE：移除授权

mysql安装与配置

安装mysql

#配置yum源
[root@YingMo ~]# cd /usr/src/
[root@YingMo src]# ls
debug  kernels
[root@YingMo src]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
[root@YingMo src]# yum -y install mysql57-community-release-el7-10.noarch.rpm
[root@YingMo src]# ls /etc/yum.repos.d/
CentOS-Base.repo  epel.repo  mysql-community.repo  mysql-community-source.repo
#可以看到已经有了mysql源了
#接下来安装mysql，安装mysql涉及四个包，分别为mysql-community-server、mysql-community-client、mysql-community-common和mysql-community-devel
[root@YingMo src]yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel

配置mysql

#先启动mysql
[root@YingMo ~]# systemctl start mysqld
[root@YingMo ~]# systemctl status mysqld
● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2019-02-15 15:00:12 CST; 8s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 26071 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
  Process: 25997 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 26075 (mysqld)
   CGroup: /system.slice/mysqld.service
           └─26075 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
Feb 15 15:00:08 YingMo systemd[1]: Starting MySQL Server...
Feb 15 15:00:12 YingMo systemd[1]: Started MySQL Server.
#确保3306端口处于监听状态
[root@YingMo ~]# ss -antl
State      Recv-Q Send-Q  Local Address:Port                 Peer Address:Port
LISTEN     0      128                 *:22                              *:*
LISTEN     0      80                 :::3306                           :::*                  
#找到临时密码
[root@YingMo ~]# grep "password" /var/log/mysqld.log
2019-02-15T07:00:09.467221Z 1 [Note] A temporary password is generated for root@localhost: g(=mj,K_r1gg
#使用临时密码登陆mysql
[root@YingMo ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
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>
#看到上面“mysql>”代表登录成功
#修改mysql登陆密码
#将密码安全性检查调到LOW
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
#将密码最大长度设置为1（因为是测试环境，所以改成了1，生产环境最好还是长一些）
mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'lynk';
Query OK, 0 rows affected (0.00 sec)
#如果不想改变validate_password_policy参数，保持默认，那么密码必须包含有数字、小写或大写字母、特殊字符
mysql> quit
Bye
#为了防止更新我们要卸掉最开始安装的yum源。因为更新后可能会存在不稳定的情况，这种问题还是能避免就避免一下的比较好。
[root@YingMo ~]# rpm -qa|grep mysql
mysql-community-common-5.7.25-1.el7.x86_64
mysql-community-libs-5.7.25-1.el7.x86_64
mysql-community-server-5.7.25-1.el7.x86_64
mysql57-community-release-el7-10.noarch
mysql-community-libs-compat-5.7.25-1.el7.x86_64
mysql-community-client-5.7.25-1.el7.x86_64
mysql-community-devel-5.7.25-1.el7.x86_64
[root@YingMo ~]# yum -y remove mysql57-community-release-el7-10.noarch

mysql工具的使用

#语法:mysql [OPTIONS] [database]
#常用OPTIONS：
-uUSERNAME   指定用户名，默认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@YingMo ~]# mysql -uroot -p -h127.0.0.1
#注意:不建议在命令行中直接使用密码登陆，因为日志系统会将用户命令记录下来，导致密码泄露。建议使用-p选项，用交互式命令输入密码。

服务器监听的两种socket地址

ip socket：默认监听在tcp的3306端口，支持远程通讯
unix socket：监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock）仅支持本地通讯
- server地址只能是：localhost，127.0.0.1

应用实例

创建一个以lynk为名的数据库，创建一张表student，该表包含三个字段（id，name，age），表结构如下

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> use lynk;
Database changed
mysql> CREATE TABLE student (id int(11),name varchar(100),age tinyint(4) NULL);
Query OK, 0 rows affected (0.20 sec)
mysql> desc student;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | YES  |     | NULL    |       |
| name  | varchar(100) | YES  |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.15 sec)

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)

往新建的student表中插入数据（用insert语句）

mysql> insert student VALUES (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);
Query OK, 11 rows affected (0.04 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)

修改lisi的年龄为50

mysql> update student set age = 50 where name = 'lisi';
Query OK, 1 row affected (0.80 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)

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 (0.03 sec)

查询student表中年龄最小的3位同学

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)

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)

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 (0.01 sec)

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 (0.02 sec)

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)

修改wangwu的年龄为100

mysql> update student set age = 100 where name = 'wangwu';
Query OK, 1 row affected (1.35 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      |  100 |
|   10 | qiuyi       |   15 |
|   11 | qiuxiaotian |   20 |
+------+-------------+------+
11 rows in set (0.00 sec)

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 = 'zhangshan' and age <= 20;
Query OK, 1 row affected (0.06 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)