Need Help Centos mysql-server

i have a problem tring too isntall mysql server and mariadb-server on centos but when i execute this code, systemctl start mariadb.service, reutrn my this mesage. Failed to start mariadb.service: Unit mariadb.service failed to load: No such file or directory.Failed to start mariadb.service: Unit mariadb.service failed to load: No such file or directory. i dont now what too do. please help me :s