In Tableau, data unions allow you to combine data from multiple tables or data sources into a single, unified dataset. This is particularly useful when you have data spread across different tables that share the same structure but contain different records. By using data unions, you can analyze all the data together as if it were in a single table.

• Definition: A data union is a method of combining data from multiple tables that have the same columns into one table.
• Use Case: Ideal for combining data from different periods, regions, or categories that are stored in separate tables but have the same schema.

• Consistent Schema: When all tables have the same columns and data types.
• Separate Data Sources: When data is stored in different files or databases but needs to be analyzed together.
• Appending Data: When you need to append rows from multiple tables into a single table.

1. Open Tableau and Connect to Data Source

   • Launch Tableau and connect to your primary data source.
   • For this example, let's assume you have two Excel files: Sales_2021.xlsx and Sales_2022.xlsx.

2. Add Data Sources

   • Click on the Data menu and select New Data Source.
   • Connect to Sales_2021.xlsx and Sales_2022.xlsx.

3. Navigate to the Data Source Tab

   • Go to the Data Source tab at the bottom of the Tableau interface.

4. Drag Tables to the Canvas

   • Drag the Sales_2021 table to the canvas.
   • Drag the Sales_2022 table to the canvas and drop it below the Sales_2021 table. Tableau will automatically create a union.

5. Verify the Union

   • Tableau will display a preview of the unioned data.
   • Ensure that the columns from both tables align correctly.

6. Rename the Union (Optional)

   • You can rename the unioned table for clarity. For example, name it Sales_Union.

Objective: Combine data from two Excel files, Sales_Q1.xlsx and Sales_Q2.xlsx, into a single dataset.

1. Connect to Data Sources: Connect to both Sales_Q1.xlsx and Sales_Q2.xlsx.
2. Create the Union: Drag both tables to the canvas to create a union.
3. Verify the Data: Ensure that the columns align correctly and the data is combined as expected.
4. Rename the Union: Rename the unioned table to Sales_H1.

Solution:

1. Connect to Data Sources:

   • Open Tableau and connect to Sales_Q1.xlsx.
   • Add a new data source and connect to Sales_Q2.xlsx.

2. Create the Union:

   • Drag Sales_Q1 to the canvas.
   • Drag Sales_Q2 below Sales_Q1 to create the union.

3. Verify the Data:

   • Check the preview to ensure columns align correctly.

4. Rename the Union:

   • Rename the unioned table to Sales_H1.

• Mismatched Columns: Ensure that all tables have the same columns and data types.
• Incorrect Data Types: Verify that the data types of columns match across all tables.
• Overlapping Data: Be cautious of duplicate records when combining data from different tables.

• Consistent Naming: Use consistent column names across all tables to avoid alignment issues.
• Data Cleaning: Clean your data before creating a union to ensure consistency.
• Documentation: Document the purpose and structure of your unions for future reference.

In this section, you learned how to create data unions in Tableau to combine data from multiple tables into a single dataset. This technique is essential for analyzing data spread across different sources with the same schema. By following the step-by-step guide and completing the practical exercise, you should now be able to effectively use data unions in your Tableau projects. In the next section, we will explore data cleaning techniques to ensure your data is ready for analysis.