Understanding Tableau Concepts15% of the exam
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.
Understand aggregations: Explain the default aggregation for measures; Describe how an aggregated measure changes when dimensions are added to a view.
~8 min read · 6 practice questions ·
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
Measure added to the view
- Detail
- Aggregated by default; the function appears in the pill name
Typical default aggregation
- Detail
- SUM, as in SUM(Profit)
Change for one view
- Detail
- The pill's context menu changes that instance only
Change for every new view
- Detail
- Data pane, right-click, Default Properties > Aggregation
No default aggregation
- Detail
- Calculated fields containing an aggregation; published data sources
Dimension aggregations
- Detail
- Minimum, Maximum, Count, Count (Distinct), plus Attribute
Count (Distinct)
- Detail
- Number of unique values; nulls ignored
"Requires extract"
- Detail
- Count (Distinct) on Access, legacy, or pre-8.2 Excel/text workbooks
MAX of a string
- Detail
- Usually last in alphabetical order
Dimensions on Rows or Columns
- Detail
- Number of marks may increase as members combine
Second measure
- Detail
- Can increase marks, but isn't a level of detail change
Sources for this section (5)
- Data Aggregation in Tableauhelp.tableau.com (opens in a new tab)
- Build a Basic View to Explore Your Datahelp.tableau.com (opens in a new tab)
- Edit Default Settings for Fieldshelp.tableau.com (opens in a new tab)
- Tableau Functions (Alphabetical)help.tableau.com (opens in a new tab)
- Dimensions and Measures, Blue and Greenhelp.tableau.com (opens in a new tab)
- 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?
The questions are free to read. Answers with their sources and self-grading are included with the pack.
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