First : need to update your source yum, yum sources to ensure the latest.
1. Install:
yum install -y mariadb-server
2. Start maria DB services:
systemctl start mariadb.service
(Note: CentOS 7.x start, CentOS start using the service instead of systemd daemon, a command related to the original management system startup and management services all replaced by systemctl command.)
3. Add mariadb service to boot from the start:
systemctl enable mariadb.service