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Data & Analytics · Foundational

Cardinality (Data Modeling)

The number of instances of one entity that can relate to instances of another: one-to-one, one-to-many or many-to-many.

Definition

Relationship cardinality determines how tables are linked and where foreign keys go. In Power BI, relationship cardinality is set as one-to-one, one-to-many, many-to-one or many-to-many. The word 'cardinality' is also used for the number of distinct values in a column.

Example

One customer places many orders, so Customer-to-Order has one-to-many cardinality.

Exam tip

Read the context: 'relationship cardinality' means 1:1, 1:N or M:N; 'high cardinality column' means many distinct values.

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