What is table calculation in Tableau?

A table calculation is computed on the aggregated result already in the view, after the query has returned, rather than in the database.

That makes it fast and flexible, but it also means a table calculation can only see what the view contains. Anything filtered out is invisible to it.

Every table calculation is defined by two things: partitioning, the dimensions it resets within, and addressing, the dimensions it moves along. A running total addressed along Month and partitioned by Region restarts at each region and accumulates through the months. Getting these the wrong way round produces a plausible but wrong chart.

Common functions include `RUNNINGSUM`, `WINDOWAVG`, `TOTAL`, `RANK`, `INDEX`, `FIRST`, `LAST` and `LOOKUP`. Quick Table Calculations from the right-click menu cover the familiar cases, but it is always worth opening Edit Table Calculation afterwards to check the addressing.