安装mysql和mysql-devel都成功，但是安装mysql-server失败，如下：
[root@localhost ~]# yum install mysql-server Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: mirrors.sina.cn * extras: mirrors.sina.cn * updates: mirrors.sina.cn No package mysql-server available. Error: Nothing to do
查资料发现是CentOS 7 版本将MySQL数据库软件从默认的程序列表中移除，用mariadb代替了
解决办法：
1. 下载mysql的repo源
$ wget http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm
2. 安装mysql-community-release-el7-5.noarch.rpm包
$ rpm -ivh mysql-community-release-el7-5.noarch.rpm
安装这个包后，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。
3. 安装mysql
$ yum install mysql-server