Marking a field “unique” in your data template will require every value in that column to be unique. If there are non-unique values in a column that must be unique, both values are highlighted as errors during the review step.
In order to validate this data and remove this error, one of the non-unique values must be changed to a unique value. This ensures that there is no duplicate data.
If Flatfile sees duplicate values in your data, it will prompt you to select which field should be merged and which field you would prefer to keep. If you would like to, you will also have the option to keep both fields and not merge the duplicate data.