直接使用yum安装默认安装的是mysql 5.1版本，要想安装mysql 5.7 需要设置yum源
1.检查系统默认mysql，并删除
yum list installed | grep mysql
yum -y remove mysql-libs.x86_642.添加rpm源,并设置最新的源（注意，yum-config-manager命令如果不存在，需要 yum install yum-utils）
wget dev.mysql.com/get/mysql-community-release-el6-5.noarch.rpm
yum localinstall mysql-community-release-el6-5.noarch.rpm
yum repolist all | grep mysql
yum-config-manager --disable mysql55-community
yum-config-manager --disable mysql56-community
yum-config-manager --enable mysql57-community-dmr
yum repolist enabled | grep mysql
3.然后就可以正常安装mysql了
yum install mysql-community-server