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Data & Analytics · Intermediate

Surrogate Key

A system-generated identifier with no business meaning, such as an auto-increment integer or GUID, used as a primary key.

Definition

Surrogate keys insulate a model from changes in business identifiers and are compact for joins. In dimensional modeling they are essential for Type 2 slowly changing dimensions, where the same business key appears in several versions of a dimension row.

Example

CustomerKey INT IDENTITY(1,1) in DimCustomer, alongside the business key CustomerNumber.

Exam tip

SCD Type 2 requires a surrogate key because the natural key repeats across historical versions.

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