plesk mysql reporting different version in cli to a version query

I'm trying to upgrade a Plesk server running Ubuntu (12.04.2 LTS) and when doing a query check on apt-cache: apt-cache policy mysql-server ... it reports that I have the latest 5.5. branch already installed. which is 5.5.52 However when I do a mysql version query command it reports a much earlier version of mysql. How could I have a difference in versions, is there more than one copy installed and if so how do I update the version on my actual domain which seems to be out of date.