在Centos的库中Mysql已经被Mariadb数据库替代，如果想继续在centos上安装mysql就需要自己下载安装包
# wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
# rpm -ivh mysql-community-release-el7-5.noarch.rpm
# yum install mysql-community-server
运行成功后重启mysql服务:
# service mysqld restart 或者 #/etc/init.d/mysqld restart
初始安装的mysql的root用户是没有密码的，配置root密码
# MySQL -uroot
mysql> set password for ‘root’@‘localhost’ = password('mypasswd');
mysql> exit
