# Tableau Prep Builder: Aggregations (Part 5 of 7)

> This is content from just-tim, the data-and-analytics channel by Tim Ngwena (formerly 'Tableau Tim'). Tim has 12+ years of hands-on BI experience and covers Tableau most of all, plus Power BI, Looker, Hex, SQL and data modelling, the analytics industry, and the craft of doing the job — always tool-agnostic and honest about the trade-offs.

- **Author:** Tim Ngwena (just-tim, https://just-tim.com/about)
- **Published:** 2020-01-27
- **Format:** Video · 8 min watch · transcript available
- **Topics:** Data prep
- **Tools:** Tableau (aggregations, prep)
- **Canonical:** https://just-tim.com/posts/tableau-prep-builder-aggregations-part-5-of-7
- **Watch:** https://www.youtu.be/HgmXiRk7yY0

I walk through the aggregation step in Tableau Prep Builder, part of my Tableau Prep for Excel users series. Using the Sample Superstore flow, I show how to group by dimensional fields, aggregate numerical and dimensional values, and explain how aggregation reshapes your data and drops unused columns.

## Key takeaways

- Unlike Tableau Desktop where aggregations happen in the view, Prep requires a dedicated aggregation step because you're reshaping row-level data into rolled-up output.
- The aggregation step uses two panes: group-by fields on the left (dimensions) and the fields being aggregated on the right (numerical values).
- Aggregating only returns the rows and columns you bring in, so to reconnect aggregated values to the original data you need a join or VLOOKUP.
- Dropping a dimensional field onto the right pane lets Prep auto-detect it and offer count, count distinct, min, max, percentile, or group-by options.
- Cleansing changes like excluding values or renaming fields are captured within the same aggregation step and surfaced in the changes column.

## Chapters

- 0:00 Setting up the sample flow
- 0:59 Why aggregations differ from Tableau Desktop
- 1:40 Adding the aggregation step
- 2:21 Grouping and aggregating fields
- 3:40 Changes column and lost columns
- 5:03 Aggregating dimensional attributes
- 6:34 Practical uses and final tips

Watch the full video, read the transcript and use chapter deep-links on the page: https://just-tim.com/posts/tableau-prep-builder-aggregations-part-5-of-7

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just-tim — Data and analytics, with a point of view. · https://www.youtube.com/channel/UC7HYxRWmaNlJux-X7rNLZyw · https://twitter.com/TableauTim · https://www.linkedin.com/in/timngwena