04 - Data Control & Prep Flashcards
Explain the difference between Live and Extract when connecting to a data source.
A Live Connection retrieves data continuously, while an Extract takes a snapshot of the data and stores it in a .hyper file.
Explain how to sync with changes made to the dataset after I went on using Extract mode.
Scenario: I took an extract from a data source and built my visualisations. After a couple of days, this data source was updated with recent information and I want to reflect it on my dashboards.
Go back to the Data Source page and click on the Refresh button next to the area where you choose between Live/Extract.
Once an extract is taken, the “live” connection to the data source is interrupted, meaning it won’t refresh automatically. This manual procedure is required when using Extract.
Explain the trade-offs in terms of performance and information security when comparing Live to Extract.
Performance
Extract performs better than Live when using large or very large datasets since it relies on snapshot from the data in time (stored in a hyper file). Querying large amounts of data continuously (Live connection) is computationally expensive, therefore hurting performance.
Information Security
Extract poses a risk from a information security standpoint compared to a Live connection. The latter has, in principle, built-in mechanisms to secure data against unauthorized access, while the forme relies on the user discretion to ensure the hyper file is securely stored.
For example, cloud-hosted (AWS, Azure, etc.) or on-premises databases are subjected to industry best-practices in terms of database management and a Live connection to it must comply with these guidelines.
Scenario: I had connected to an Excel file, created some dashboards and uploaded them to Tableau Public. A couple of days later, I want to resume working on it so I’ve downloaded it from Tableau Public as a workbook (.twbx). Note: I am using Tableau Public instead of the Desktop version.
How can I restore the connection to my original data source file from this workbook file?
This .twbx file is not connected to the data source when I open it. It has the necessary data to render the visualisations, though.
To re-connect it to the original data source, I need to go to the Data Pane on one of the sheet, then right-click and choose Edit Data Source. Select the original file and Tableau will re-connect to it.
