Vtiger provides you the following three options in Webforms to handle duplicate records:
- Keep existing value - Retains the existing values in the CRM. If no value exists in a field, then the submitted value is considered.
- Use non-blank submitted value - Replaces the value in the CRM value with the submitted value.
- Append to existing data - Appends the submitted value to the value existing in the CRM. In this case, you must configure a Concatenation Separator to tell the submitted value apart from the CRM value. You can set it up under Settings > Configuration > Configuration Editor.
To learn more about Webforms, click here.