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About this lesson
This lesson focuses on the characteristics that are required in order to link tables together properly, as well as a key tip that will prevent getting yourself into trouble later.
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Key Concepts for Relating Data
Key concepts you should know before relating data.
When to use
When you are getting ready to link two or more tables together in the data model.
Power BI only supports two types of relationships: one to many, and one to one
One to Many relationships
- The relationship column on the One side of the relationship MUST contain UNIQUE values
- The relationship column on the Many side of the relationship MAY contain REPEATING values
- When linking in relationship view, drag and drop will NEVER get this relationship backwards
- Ensure you are using a single direction filter (the arrow points to the many side only)
One to One relationships
- The relationship column in BOTH tables MUST contain UNIQUE values
- This relationship may need to be modified to get it correct
- This relationship type MUST use a bi-directions filter (the arrows point both directions)
- These relationships can often be built using a one to many relationship
Hints & tips
- Bi-directional filters (double headed arrows) can cause issues. Avoid them unless they are required for a specific reason (most of the time they are not).
- Hide the many side of the relationship from the model to prevent future filtering errors
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