Stop data inserting into a database twice

Question

I was wondering what methods/preventions other programmers use to stop data being entered twice into a MySQL database when a user refreshes on the same page as a form? Obvio

Answer 1

Well, first of all, to minimize, you should make it so they have to do form post to insert the data. That way, at least they will get that nice little confirmation dialog asking if they really want to resubmit it.

To get more complicated than that, you could put a hidden one time use key in each form, and once the form with that key has been submitted, display an error when they try to submit a form with the same key. To create this key, you probably want to use something like a GUID.