yum remove mariadb mariadb-server
rm -rf /var/lib/mysql If your datadir in /etc/my.cnf points to a different directory, remove that directory instead of /var/lib/mysql
rm /etc/my.cnf the file might have already been deleted at step 1
Optional step: rm ~/.my.cnf
rm -f /var/log/mariadb
rm -f /var/log/mariadb/mariadb.log.rpmsave
rm -rf /usr/lib64/mysql
rm -rf /usr/share/mysql