第一步：安装从网上下载文件的wget命令
[root@master ~]# yum -y install wget
第二步：下载mysql的repo源
[root@master ~]# wget http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm
第三步：安装mysql-community-release-el7-5.noarch.rpm包
[root@master ~]# rpm -ivh mysql-community-release-el7-5.noarch.rpm
第四步：查看下
[root@master ~]# ls -1 /etc/yum.repos.d/mysql-community* /etc/yum.repos.d/mysql-community.repo /etc/yum.repos.d/mysql-community-source.repo
会获得两个mysql的yum repo源：/etc/yum.repos.d/mysql-community.repo，/etc/yum.repos.d/mysql-community-source.repo。
第五步：安装mysql
[root@master ~]# yum install mysql-server