vi  /etc/yum.repos.d/MariaDB.repo

# MariaDB 10.3 CentOS repository list - created 2019-01-30 12:36 UTC
# http://downloads.mariadb.org/mariadb/repositories/
[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.3/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

yum update