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1. Save your workbook as a .twbx file to ensure the workbook will contain the extracted data
2. Create a list-type string parameter, call it something like "zEmpty"
3. Add two items of your choosing, but for this, we shall use "T" and "F"
4. Now create a calculated field to materialise the output of the zEmpty parameter, call it something useful like zEmptyExtract, and either drag the parameter to the field, or type it's name in the calculated field to materialise it
5. Now, set your parameter value to "T" (or whatever you have used)
6. Right-mouse select the connection you want to convert to an extract
   1. Select Extract Data from the context menu
7. Now we add a filter:
   1. Press the Add... button beneath the filters box
   2. Add the "zEmptyExtract" field
   3. Select "T" or whatever value you chose to represent this
   4. CRUCIALLY now choose exclude to ensure only those fields that do not have the value of 'T' are brought through - all of the data in your source will be marked as 'T' so none of the fields will be transferred
   5. Press OK to add the filter
   6. Press Extract to begin the extraction - this will be complete in a split-second as no data will be transferred
8. Now save your workbook to ensure the extract is built
9. CRUCIALLY change the ZEmpty parameter to anything but "T" so all fields will now have this new value allowing "T" to remain as an exclusion
10. Save your workbook once more
11. Upload your workbook to your Tableau Server
12. Set an immediate refresh so Tableau will now extract all the data

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