Create default database/table on Rails 3 app

Hi!

I'm creating an app where I need to compare the user input with a
default database and give the corresponding value (something like what
the Lookup function does in spreadsheets). For that I need to things
that I don't understand...

1.- How can I create a default database (or table) for production?
Should I use fixtures for that?

2.- How can I compare two values from the table? In my case is to
look for an age and the give back kcal/day requirements; I believe in
symphony I'd use something like those magic methods, findBy* or
findbyOne*, but I don't know how to do something similar in rails...
there's such a magic method?

I hope you can guide me! :slight_smile: