A definition and two questions

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, or 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 and the available RAM on your machine to execute computational tasks; however, after that work is completed and a dataset is returned, Tableau performs additional processing before rendering the results.

Let us look at the definition of table calculations, as follows:

A table calculation is a function performed on a cached dataset that has been generated as a result of a query from Tableau to the data source.

Let's consider a couple of points regarding the dataset in cache mentioned in the preceding definition:

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