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

I'd agree with Ilya there and add that you should use some client javascript to disable the 'submit' button once it's been clicked or present a modal dialog (css can help you here) to avoid multiple clicks on the submit button.

Lastly, if you don't want the data in your database twice then also check your database for the data before you try to insert it. If you do allow duplicate records but don't want rapid repeat insertions from a single source then I'd use a time/date stamp and IP address fields to allow for a time-based 'lockout' in my submission code, i.e. if the IP is the same and the last submission time was less than 5 minutes ago then don't insert the new record.

Hope that gives you some ideas.