How To allow my users to update their field ?

Hello all,
I skimmed trough "all" the forum but I didn't find the answers of my questions but I'm sure the answer is simple.
I use forms to allow my users to register for sports tournaments. I would like to allow them, to update their registration.
In other terms, I'd like to know how can I implement an UPDATE instead of a INSERT INTO.

Today, when a user submit a form, it created a new entrie in the database. If he submitted 5 times the form, it created 5 entries. I want to have only 1 entries

thanks to all for your answers

Hi Yann63,

Make sure that the Primary Key value of the record that you want to update is included in the form as a hidden input. Something like:

<input type='hidden' name='cf_id' value ='9999' />

Bob