How do you approach the data from DynamoDB tables into Tableau?
Web Data Connector? Hive? Redshift? Just curious.
With the latter two it would be possible to use Custom SQL
to add calculated columns to the data (without modifying the source).
I'm using CData's ODBC.
There should be a 'New Custom SQL' button
in the lower left of the Tableau Datasource Pane.
If so, then you're able to write a Custom SQL code
as a datasource object (dataset).
Besides, there should be also a menu option
Data --> Convert to Custom SQL
which may help with the initial creation
of the datasource-specific code
directly from the existing table object.
You may want to add a new calculated column
to that code using the familiar syntax.