I am not sure how you are unioning the data (combining the data).There are multiple ways of doing this like joins,blends,sets etc in tableau.
you can use the datasource attributes and get the needed details.check the below.
if you can attach a workbook with dummy data we can help you out.
hope it helps.
Attached is a sample of what I'm trying to do. It contains two xlsx and one csv files. The common dimension between them is a "Host". I want to be able to list the Data Source filename (or source sheet) that the "Host" appears on.
Practical application: I am combining several sheets of data, that have one dimension in common. Each sheet has distinct information, and even the name of the sheet is important to know and correlate for reference. If the "Host" exists on sheets "A" and/or "B", that's important information for me to know.
Hi Like Like,
I don't find any attachments in your reply.