You can now ensure that all newly created database records are unique by choosing to check for duplicates. To enable this feature, navigate to your database, select Options > Edit (Database Actions) > Edit Existing Fields. Select the "Prevent Duplicates" box for each field that should be unique, and click Update.
Once enabled, if new records contain duplicate data in fields marked as "Chk Dup," the following message will warn users and provide them with links to the duplicate records. From this window, users can proceed to save anyway or cancel the save and revise the record.
You can also completely restrict users from saving duplicate records. To prevent duplicate records from being created, navigate to your database, select Options > Edit (Database Actions), choose "No" under the "Allow Duplicates?" option, and click Save Changes.
Note: This setting works in conjunction with the "Chk Dup" feature. So just setting this option to "No" without checking for duplicates will not do anything.