WILDCARD UNIONS
As you have previously seen, the subfolder South contains three more files with the same data structure; each file contains data for a different year, but they all have the same columns and column headers. You would like to integrate these into the workflow to create one table containing the data for all four years. In other words, you would like to union the data.
With just one other file or data source, you could add another connection and drag it onto the flow, as you did in Tableau Desktop in Chapter 2. You will try this approach in Tableau Prep later.
However, with multiple files, you can save time by using the wildcard union feature. More important, using wildcard unions ensures that files added to the folder in the future will automatically be included when you re‐run the flow.
To do this, click the Multiple Files tab in the Input area. Choose the Wildcard Union option, as shown in Figure 10.5. At the bottom is a list of files that are included in the folder...
