Selecting one value from database?

[eluser]fancms[/eluser]
Thank you both, Rafael and xwero; it makes a lot more sense now

One more question - since this is a function I'd definitely want to reuse, is it something I could make into a plugin / helper? How would I go about running the database queries from an external function file like that? When I tried saving it as a plugin, loading it in the controller file, and running the function, I got the message:

Fatal error: Using $this when not in object context