It's honestly not hard to change over, as long as you're careful. I'd just build the new pet table with an ID, migrate the data across and then double check everything still works...which it won't at first
but you have to start somewhere! DB's are a lot easier to deal with than people think, you just need to be careful! (disclaimer: I've been working with databases for 6 years now and they've asked us to do some of the most sketchy, nerve wracking things you can do with a database...but it always ends up working!)