An overview of table calculations
Table calculations are different from all other calculations in Tableau. Row-level, aggregate calculations, and LOD expressions, which we explored in the previous chapters, are performed as part of the query to the data source. If you were to examine the queries sent to the data source by Tableau, you'd find the code for your calculations translated into whatever implementation of SQL the data source used.
Table calculations, on the other hand, are performed after the initial query. Here's a diagram that demonstrates how aggregated results are stored in Tableau's cache:
Figure 6.1: Table calculations are computed in Tableau's cache of aggregated data
Table calculations are performed on the aggregate table of data in Tableau's cache right before the data visualization is rendered. As we'll see, this is important to understand for multiple reasons, including the following:
- Aggregation: Table...