The default data blending join in Tableau functions as a left outer join, where all records from the primary data source are included and only matching records from secondary sources are brought in.
Practical Response 1:
“By default, data blending works like a left join—it keeps all my primary data and pulls in matching information from secondary sources, dropping any secondary data that doesn’t match.”
Practical Response 2:
“When I blend data, Tableau automatically uses a left join approach. This means I get all records from my main data source and only the matching records from my secondary sources, which is usually what I need for my analysis.”
Detailed Explanation:
Tableau’s default blending behavior mirrors a left outer join operation, where:
- All records from the primary data source (displayed with a blue checkmark) are preserved in the results
- Only matching records from secondary data sources (displayed with orange checkmarks) are included
- Non-matching records from secondary sources are excluded from the blended dataset
- The relationship is established through linked fields that share common dimension values
This default behavior can be modified by:
- Changing which data source is designated as primary
- Applying filters to remove null values from the primary source
- Using context filters to limit the primary dataset
- Creating calculated fields to handle missing matches
The left-join approach ensures that your primary analysis remains intact while supplementing it with additional metrics from secondary sources, making it particularly useful for scenarios like adding budget figures to actual sales data or enriching customer records with demographic information.
Keywords:
- default data blending Tableau
- left outer join Tableau
- primary data source Tableau
- secondary data sources
- data blending relationships
What is the default Data Blending Join in Tableau?