Upgrade MySQL to 5.5 in CentOS 6

The answer is install Remi.

1. Install Remi dependency

For 64bit
rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-7.noarch.rpm

For 32bit
rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-7.noarch.rpm

2. Add Remi

rpm -Uvh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm

3. Test if MySQL 5.5 is now available

yum --enablerepo=remi,remi-test list mysql mysql-server

4. Update or install

yum --enablerepo=remi,remi-test update mysql mysql-server

or

yum --enablerepo=remi,remi-test install mysql mysql-server

5. Restart/Start MySQL and check for errors.

mysql_upgrade -u username -p