第一步：安装从网上下载文件的wget命令

yum -y install wget

第二步：下载mysql的repo源

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

rpm -ivh mysql-community-release-el7-5.noarch.rpm

第四步：查看下

ls -1 /etc/yum.repos.d/mysql-community*

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

yum install mysql-server