Live Connections vs. Extracts: Choosing the Right Data Source

The Core Concept: Live vs. Extract

At a high level, the choice is simple and can be understood with an analogy. A live connection is like streaming a movie: you need an active internet connection to the source, and you're always getting the most current version. A data extract is like downloading that movie: you create a local copy that you can watch anytime, anywhere, even offline, but it won't include any new scenes added after you downloaded it.

This diagram visually represents the two different data flows:

Now, let's watch a short video that explains this core trade-off between performance and data freshness.

To summarize:

• Live Connection:

  • How it works: Tableau sends queries directly to your original data source (e.g., your Excel file or a corporate database).
  • Pro: The data is always up-to-date. Any changes in the source data are reflected in your dashboard (after a refresh).
  • Con: Performance depends entirely on the speed of the source data system. Large datasets or slow databases can result in slow dashboards.

• Data Extract (.hyper file):

  • How it works: Tableau takes a snapshot of the data and saves it as a highly compressed and optimized file (with a .hyper extension) on your computer. Your workbook then queries this local file.
  • Pro: Performance is typically much faster, as the data is optimized for Tableau. You can also work on your data offline.
  • Con: The data is static. It is only as fresh as the last time you created or refreshed the extract.

A Practical Demonstration

Now that you understand the theory, let's see how this works in practice. We'll use a video that demonstrates the process using an Excel file, building directly on what you learned in the previous lesson.

The video will show you:

1. How a live connection reflects changes made to the source Excel file.
2. How to switch to an extract.
3. How an extract does not automatically reflect changes and must be manually refreshed.
4. The visual icons in Tableau that tell you which connection type is active.

This hands-on view is crucial. The simple act of switching between the 'Live' and 'Extract' radio buttons on the Data Source page fundamentally changes how your workbook interacts with its data.

When to Choose Live vs. Extract

You now know the "what" and the "how." The final piece is the "when"—choosing the right connection for a given scenario. This decision is a strategic one that you'll make in your future role as an analyst.

Here is a summary to guide your decision-making:

To deepen your understanding of these use cases, let's look at a more detailed article.

As someone planning to use Tableau Public, you will primarily use data extracts. When you upload a file (like a CSV or Excel file) to Tableau Public, it is essentially creating an extract that is stored on the Tableau server. This is one reason why Tableau Public is so fast and performant. Live connections are more common in enterprise environments with direct connections to company databases.

Your Turn: Hands-On Practice

Let's apply what you've learned.

1. Open Tableau.
2. Connect to the Sample - Superstore Excel file, which you can find in your My Tableau Repository/Datasources folder.
3. On the Data Source page, ensure the Live connection option is selected in the top-right corner.
4. Go to any worksheet by clicking the "Sheet 1" tab at the bottom.
5. In the Data pane on the left, notice the icon next to your "Sample - Superstore" data source. It should be a single gray cylinder.
6. Now, go back to the Data Source tab at the bottom.
7. Change the connection type to Extract.
8. Go back to "Sheet 1". Tableau will prompt you to save the extract file. Name it Superstore_Extract and save it.
9. Look at the icon next to the data source in the Data pane again. It should now be a double cylinder with an arrow, indicating it's an extract.

This simple exercise helps you practice switching between connection types and reinforces the visual cues within Tableau.

Conclusion

Excellent work! You've mastered a fundamental concept that separates beginner and intermediate Tableau users. Making a deliberate choice between a live connection and a data extract is key to building effective and efficient dashboards.

Key Takeaways:

• Live Connection: Offers real-time data but can be slow. Your dashboard's performance is tied to the source database.
• Data Extract: Offers fast performance and offline access by using a local, optimized snapshot of the data. The data is static until you refresh the extract.
• The Choice is a Trade-off: You must balance the need for data freshness against the need for performance and portability.
• Visual Cue: A single cylinder icon means 'Live', while a double-cylinder icon means 'Extract'.

Preview of the Next Lesson:

Now that your data is connected and your connection type is set, the next step is to understand the building blocks of your dataset. In our next lesson, you will learn to differentiate between dimensions and measures. This is the foundation for turning your raw data into meaningful visualizations.