Apart from depeneding on the Repository source. You can try following
sudo apt-get update && sudo apt-get upgrade
Then search for the package using apt-cache.
sudo apt-cache search mysql | grep mysql | more
You will have couple of results and you can choose appropriate one for you. You might need the client or Server (depends on your needs). The result is as below:
mysql-server - MySQL database server (metapackage depending on the latest version)
mysql-server-5.5 - MySQL database server binaries and system database setup
mysql-client - MySQL database client (metapackage depending on the latest version)
mysql-server - MySQL database server (metapackage depending on the latest version)
mysql-client-5.5 - MySQL database client binaries
Once you figure out what version of sql is available. You can install it with apt-get.
sudo apt-get install mysql-server mysql-client
Hope this helps. Alos this is the official Mysql Community page to download MySQL Server for different platforms.