To maintain the integrity of your data, it’s a good idea to have rules in place to reduce duplicate records in the system.
Create a duplicate detection rule
1. Make sure you are a member of a team with 'Duplicate Rules' security role.
2. Go to form explorer.
3. Select the form you want to create the duplicate rule for, then click on 'Rules -> Duplicate Rules' menu item from the toolbar.
The duplicate rule designer opens with a single rule created for you.
5. Add a rule name in the description box.
6. Add rule. To Add rule:
a. Select a field from the list
b. Select operator
c. Enter message to show to the user
See duplicate rule in action.