In Tableau, you can import multiple XLS or CSV files and combine them into a union so that data from all files appears together as a single dataset. Here’s a step-by-step guide to help you do it:

 Step 1: Connect to Your Files
1. Open Tableau and go to the Data pane.
2. Select Microsoft Excel (for XLS/XLSX files) or Text File (for CSV files).
3. Navigate to the folder containing your data files and select the first file.
4. Click Open to load the data into Tableau.

 Step 2: Use Wildcard Union (If Files Have Similar Structure)

If all the files have the same structure (same columns), you can use a Wildcard Union to automatically import and combine all files in the folder:

• In the Connections pane on the left, select the Union option.
• Choose Wildcard (automatic) for the union type.
• Specify the matching pattern in the Match files by name field to include only relevant files. For example:
  •  To include all CSV files: `.csv`
  •  To include files with specific names: `sales_.csv`
• Tableau will automatically union all files that match the specified pattern and add them to the data source.

 Step 3: Manually Add Additional Files to the Union (If Necessary)
If the Wildcard Union is not suitable (e.g., files are in different folders or have varying names), you can manually add each file to the union:

1. Drag the first sheet of the first file into the Canvas area in the data source tab.
2. Hover over the sheet, click the drop-down arrow, and select Union….
3. In the Union dialog, click Add and select additional files to include in the union.
4. Click OK when done.

 Step 4: Verify and Clean Up Data
1. Tableau will create a combined view of all the files in a single table.
2. Preview the data to ensure it’s correctly combined.
3. If needed, go to the Data Interpreter option to help with cleaning if there are headers or footers in the files.

 Step 5: Start Using the Data in Tableau
Once your union is set up, you can start creating visualizations and dashboards in Tableau using the combined dataset.

By following these steps, you’ll have a unified dataset from multiple XLS/CSV files in Tableau, ready for analysis.