InfoPath Dev

How I can refresh database every time after user fill the form? i made validation to the text field that won't allow duplication. but the problem is the user still can input the same thing that already exist in database. the duplication can be avoided after i refresh the database manually. can someone suggest me solution?

i'm trying to use coding to make a validation for text field so user won't enter same number that already exist in database. so i need help on how to write validation code using xml coding to avoid duplication.

How can i reload the form so all the text fields inside the form will be blank and user can fill the form again? is it need to use coding or button?

How do i write the code for button so the page will refresh and blank the form without putting the Submit button?