Applies to Write-Back Server and Write-Back Cloud
Question
How can I update existing data with Write-Back?
When you are using Tableau sometimes you want users to be able to send the new information straight from the dashboards the users are visualizeingvisualizing. However, Tableau is a one-way data stream, which means that any change that you perform in Tableau will not be reflected in the underlying data.
Write-Back can really help you with this, although Write-Back does not actually update the underlying data (if you want to know why you have more information here), it is easy to implement a solution that simulates this operation while still keeping your data governed and secure.
Answer
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The attached workbook has the full solution implemented and is using Writeusing Write-Back public demo environment, for more information on using it check our Public Demo instruction page.
Attachments & Related Links
Why Writing to a Separate Dataset? Tableau: Relationships Update Underlying Data.twbx
Step 1: Create a table visualization
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So, the first step is to create a table at the minimum level of granularity you want to overlap.
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The right column identifies how many rows the data set has for the product name / order date combination. These two fields will act as a the business keys.
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You configuration should look like this:
Primary Keys in the Write-Back Source Fields
New Input Fields - e.g. Quantity or Sales
Keep Write-Back in Form View
Step 3: Join with existing data
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For this you can use Tableau relationships and connect your existing data with the Write-Back dataset using the keys defined.
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Don't forget to filter Write-Back table by IsActive set to True to ensure you only get the latest snapshot provided by the users for each record.
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This calculated field has the function of verifying whether there is a value for that primary key or not on Write-Back:
If there is a value, the report show the value from Write-Back
otherwise it shows the original value
This way you get the best of both worlds, a well governed dataset for manual inputs and the end result looks like an update on the original data.
Optionally, you can display if a field was updated or not by creating another calculated field.
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Step 4: One-to-One updates
Another factor that you should keep in mind is that:
You can perform multiple updates for a specific key and to show only the most recent, you need to create a new calculated field with an LOD expression.
In alternative you can activate Write-Back setting of Unique Entries and this way Write-Back will ensure there is only one update per entry and regular calculated field will always work.
You can really choose the option that best suites your use case.
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