If you need to check what version of MySQL you have on a certain server, run either of the following commands from your command line:

select version();

or

show variables like 'version';

The first one returns a single column with the version number, and the second one return a two-column table. First column contains the variable it found (version) and the second column is the version number. Note! version() is a function.

Padding the variable with some HTML, I guess it looks impressive with “Powered by MySQL version blablabla” somewhere in your footer.