The Aggregate Step

The Context for Aggregation

An aggregate step in Tableau Prep is used to change the level of detail of data so it’s less granular, often in preparation for being combined with other data at a higher level of aggregation.


How to Aggregate

First, we need to add an aggregate step in the flow. Click the plus on the previous step and select Add Aggregate. The aggregate pane opens below, allowing us to configure this aggregation.

On the left, we see the list of fields in this data source. On the right, we have two drop areas, one for grouped fields and one for aggregated fields. In order for a field to “come out the other side” of an aggregation step, it must either be grouped or aggregated.


Grouped fields determine the granularity of the row. If we want our post-aggregation data to be the number of books sold per date, we would group by book and date. If we want our post-aggregation data to simply be the book (which we do), we’d group only by book.

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