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Data & Analytics · Foundational

One-to-Many Relationship (1:N)

A relationship where one row in a parent table can relate to many rows in a child table, but each child relates to one parent.

Definition

It is the most common relationship type and is implemented by placing the parent's primary key as a foreign key in the child table. In star schemas, each dimension has a one-to-many relationship to the fact table.

Example

One Department has many Employees; Employees.DeptID references Departments.DeptID.

Exam tip

In Power BI, the dimension is on the 'one' side and the fact table on the 'many' side; filters flow from one to many by default.

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