环境
OS：CentOS7.6
Mysql：Mysql5.7

1. 获取更新包
   Mysql官网:https://dev.mysql.com/
   到http://dev.mysql.com/downloads/repo/yum/ 去下载rpm包更新一下。

   #下载mysql源安装包
   wget http://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm
   #安装mysql源
   yum localinstall mysql57-community-release-el7-8.noarch.rpm
   #检测源是否安装成功
   yum repolist enabled | grep "mysql.*-community.*"

   

2. 安装
   修改配置yum 安装mysql的版本，这里安装MySQL5.7版本，修改“enabled=1”。
   vim /etc/yum.repos.d/mysql-community.repo

   #Enable to use MySQL 5.6
   [mysql56-community]
   name=MySQL 5.6 Community Server
   baseurl=http://repo.mysql.com/yum/mysql-5.6-community/el/7/$basearch/
   enabled=0
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
   [mysql57-community]
   name=MySQL 5.7 Community Server
   baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
   enabled=1
   gpgcheck=1
   gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql

   yum安装

   yum install mysql-community-server

   systemctl start mysqld //启动mysql服务
   systemctl status mysqld
   systemctl enable mysqld
   systemctl daemon-reload //重载服务

3. 配置
   mysql5.7安装时会产生一个默认密码，查看此密码的文件一般存在于/var/log/mysqld.log上。
   grep 'temporary password' /var/log/mysqld.log
   
   登录mysql
   mysql -uroot -p
   
   可看到mysql5.7版本默认登录后要求修改密码，采用了密码机制，默认为medium，要求密码有大写字母及特殊字符。
   修改密码：

   mysql> set password for 'root'@'localhost'=password('xxxxxxxx');

   查看密码策略：

   mysql> show variables like '%password%'

   
   0 => LOW，1 => MEDIUM，2 => STRONG
   命令行修改：
   set global validate_password_policy=0; //设置密码策略等级
   set global validate_password_length=6； //设置密码最小长度
   重启mysql服务
   systemctl restart mysqld