MySQL 5? (Along with PHP 5)

I asked yesterday whether WordPress would be effected if I moved from PHP 4 to PHP 5, I was reassured that it would be no problems. I asked my host about the PHP 5 server specs, and one of the servers is running MySQL 5 also. My current server is running MySQL 4. Would WordPress be effected if I move to the MySQL 5 server? Are there any upgrade procedurs that needs to be done? Thanks!