As discussed in Chapter 1, Getting Up to Speed – A Review of the Basics, calculated fields can be categorized as either row-level, aggregate-level, and table-level. For row- and aggregate-level calculations, the underlying data source engine does most (if not all) of the computational work and Tableau merely visualizes the results. For table calculations, Tableau also relies on the underlying data source engine to execute computational tasks; however, after that work is completed and a dataset is returned, Tableau performs additional processing before rendering the results.
The following process-flow diagram shows were the table calculations are being performed:
Let us look at the definition of table calculation, in the following information box: