So you want to install MariaDB 5.5 on Centos 6 x86_64. This is the process I used. MariaDB can be a replacement for MySQL.

Login to Centos 6 server you want to install MariaDB.

Create a repo file.

# vi /etc/yum.repos.d/MariaDB.repo and add the information below.

[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/5.5/centos6-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

# yum update

# yum install MariaDB-server MariaDB-client

# /etc/init.d/mysql start or # service mysql start

If you want to know more about MariaDB then go to their website.

https://mariadb.org/