# Extract aggregation, filters and incremental refresh

*Tableau Consultant Study Guide · Plan and Prepare Data Connections · Last updated November 3, 2026 · https://www.certifyforce.com/study-guide/tableau-consultant/plan-and-prepare-data-connections/extract-aggregation-filters-and-incremental-refresh*

Set the aggregation level and refresh strategy for extracts and flows: Aggregate data for visible dimensions and date roll-up, the filter-aggregate-then-Top N order, full versus incremental refresh, the 2024.2 minimum date range and how Tableau counts it, the 3-decimal time precision trap, Aggregate Measures in views, and Prep Aggregate steps before output.

- Certification: Salesforce Tableau Consultant
- Exam section: Plan and Prepare Data Connections
- Study guide: https://www.certifyforce.com/study-guide/tableau-consultant

**Official exam objective:**

> Specify aggregation level and strategy for data sources in Tableau products (Tableau Desktop, Tableau Prep, Tableau Cloud, Tableau Server).

## What the exam expects

- Predict the rows an extract will hold with Aggregate data for visible dimensions, date roll-up, extract filters and Top N.
- Choose between full and incremental refresh, pick the column that identifies new rows, and know what blocks incremental refresh.
- Configure the 2024.2 minimum date range to refresh and calculate exactly which periods Tableau re-extracts.
- Explain duplicate rows caused by datetime precision beyond 3 decimal places.
- Reduce rows where the work happens: Aggregate Measures in a Desktop view, or an Aggregate step before a Tableau Prep output published to Tableau Server or Tableau Cloud.

Key terms:
- **Aggregate data for visible dimensions:** an extract option that stores measures at their default aggregation for the visible dimensions.
- **Roll up dates:** an aggregation option that truncates dates to a level such as Year or Month before aggregating.
- **Incremental refresh:** a refresh that adds rows newer than the last refresh, identified by one column.
- **Minimum date range to refresh:** the 2024.2 subrange setting that re-extracts recent, already extracted rows.
- **Aggregate step:** a Tableau Prep step that groups fields and aggregates others to change the flow's granularity.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Row-count order | Filters and aggregation first, then All rows or Top N | [Extract Your Data](https://help.tableau.com/current/pro/desktop/en-us/extracting_data.htm) |
| Aggregation options | Visible dimensions; optional Roll up dates | [Extract Your Data](https://help.tableau.com/current/pro/desktop/en-us/extracting_data.htm) |
| Physical Tables storage | Disables extract filters, aggregation, Top N, sampling | [Extract Your Data](https://help.tableau.com/current/pro/desktop/en-us/extracting_data.htm) |
| Default refresh | Full refresh replaces all rows | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Incremental prerequisites | All rows; no sample; no aggregation | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Non-unique key column | Supported for incremental refresh from 2024.1 | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Minimum date range | 2024.2+; current unit plus N earlier units | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Source structure change | Full refresh before incremental can resume | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Time precision | Up to 3 decimal places in the data engine | [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm) |
| Slow disaggregated view | Select Analysis > Aggregate Measures | [Efficient Calculations](https://help.tableau.com/current/pro/desktop/en-us/perf_efficient_calcs.htm) |
| Prep granularity | Aggregate step: Grouped Fields and Aggregated Fields | [Aggregate, Join, or Union](https://help.tableau.com/current/prep/en-us/prep_combine.htm) |

## Check yourself

- Why can a Top N extract return fewer distinct positions than expected?
- When must a .tde extract be upgraded to .hyper?
- Where does Desktop show whether past refreshes were full or incremental?
- Which key column types offer the optional minimum date range?

## Sources

- [Extract Your Data](https://help.tableau.com/current/pro/desktop/en-us/extracting_data.htm)
- [Refresh Extracts](https://help.tableau.com/current/pro/desktop/en-us/extracting_refresh.htm)
- [Data Aggregation in Tableau](https://help.tableau.com/current/pro/desktop/en-us/calculations_aggregation.htm)
- [Create Efficient Calculations](https://help.tableau.com/current/pro/desktop/en-us/perf_efficient_calcs.htm)
- [Aggregate, Join, or Union Data](https://help.tableau.com/current/prep/en-us/prep_combine.htm)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 7 linked practice questions, and unlimited timed mock exams are included with the Tableau Consultant pack (USD $19): https://www.certifyforce.com/practice-exams