# Default aggregation and level of detail

*Tableau Desktop Foundations Study Guide · Understanding Tableau Concepts · Last updated October 29, 2026 · https://www.certifyforce.com/study-guide/tableau-desktop-foundations/understanding-tableau-concepts/default-aggregation-and-level-of-detail*

Why a measure lands in the view as SUM, how to change its aggregation for one view or for every view, which aggregations a dimension accepts, and how each dimension you add splits an aggregate into more marks while a second measure leaves the level of detail alone.

- Certification: Salesforce Tableau Desktop Foundations
- Exam section: Understanding Tableau Concepts
- Study guide: https://www.certifyforce.com/study-guide/tableau-desktop-foundations

**Official exam objective:**

> Understand aggregations: Explain the default aggregation for measures; Describe how an aggregated measure changes when dimensions are added to a view.

## What the exam expects

- State the default aggregation Tableau applies to a measure dragged into the view, and read it from the pill.
- Change a measure's aggregation for one view on the shelf, or for every new view with Default Properties > Aggregation, and pick the right one for a requirement.
- Name the aggregations a dimension accepts (Minimum, Maximum, Count, Count (Distinct), Attribute) and predict their results, including Count (Distinct) against Sum and Count.
- Predict how many marks a view has and what each aggregated value means as dimensions are added to Rows, Columns or the Marks card, and why a second measure doesn't change the level of detail.

Key terms:
- **Aggregation:** a function that turns a set of values into one value, such as SUM or AVG.
- **Default aggregation:** the aggregation Tableau uses automatically when a measure is first added to a view.
- **Level of detail:** how granular the view is, set by the dimensions in it.
- **Mark:** one visual item in the view; in an aggregated view, one per combination of dimension members.
- **Attribute (ATTR):** an aggregation that returns the value when every row in the group has one value, otherwise an asterisk.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Measure added to the view | Aggregated by default; the function appears in the pill name | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| Typical default aggregation | SUM, as in SUM(Profit) | [Build a Basic View to Explore Your Data](https://help.tableau.com/current/pro/desktop/en-us/getstarted_buildmanual_ex1basic.htm) |
| Change for one view | The pill's context menu changes that instance only | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| Change for every new view | Data pane, right-click, Default Properties > Aggregation | [Edit Default Settings for Fields](https://help.tableau.com/current/pro/desktop/en-us/datafields_fieldproperties.htm) |
| No default aggregation | Calculated fields containing an aggregation; published data sources | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| Dimension aggregations | Minimum, Maximum, Count, Count (Distinct), plus Attribute | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| Count (Distinct) | Number of unique values; nulls ignored | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| "Requires extract" | Count (Distinct) on Access, legacy, or pre-8.2 Excel/text workbooks | [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm) |
| MAX of a string | Usually last in alphabetical order | [Tableau Functions (Alphabetical)](https://help.tableau.com/current/pro/desktop/en-us/functions_all_alphabetical.htm) |
| Dimensions on Rows or Columns | Number of marks may increase as members combine | [Dimensions and Measures, Blue and Green](https://help.tableau.com/current/pro/desktop/en-us/datafields_typesandroles.htm) |
| Second measure | Can increase marks, but isn't a level of detail change | [Dimensions and Measures, Blue and Green](https://help.tableau.com/current/pro/desktop/en-us/datafields_typesandroles.htm) |

## Check yourself

- Why can't you change the default aggregation of a measure from a published data source?
- When does Count (Distinct) show "Requires extract"?
- Why can a tooltip show an asterisk for a dimension?
- What does MAX return for a date field?

## Sources

- [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm)
- [Dimensions and Measures, Blue and Green](https://help.tableau.com/current/pro/desktop/en-us/datafields_typesandroles.htm)
- [Build a Basic View to Explore Your Data](https://help.tableau.com/current/pro/desktop/en-us/getstarted_buildmanual_ex1basic.htm)
- [Edit Default Settings for Fields](https://help.tableau.com/current/pro/desktop/en-us/datafields_fieldproperties.htm)
- [Control the Appearance of Marks in the View](https://help.tableau.com/current/pro/desktop/en-us/viewparts_marks_markproperties.htm)
- [Tableau Functions (Alphabetical)](https://help.tableau.com/current/pro/desktop/en-us/functions_all_alphabetical.htm)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 6 linked practice questions, and unlimited timed mock exams are included with the Tableau Desktop Foundations pack (USD $19): https://www.certifyforce.com/practice-exams