centos7自帶是mariadb，一個mysql的變種。

查看有沒有安裝過：
yum list installed mysql*
rpm -qa | grep mysql*

安裝mysql軟件（mariadb）

yum install mysql*

啟動mysql
systemctl start mariadb.service 或者 systemctl start mysqld.service

結束
systemctl stop mariadb.service 或者 systemctl stop mysqld.service

重啟
systemctl restart mariadb.service 或者 systemctl restart mysqld.service

開機自啟
systemctl enable mariadb.service 或者 systemctl enable mysqld.service

centos7.0查看有沒有運行mysql