A retail organization is designing a star schema to track daily sales. Analysts discover that a single customer can participate in multiple loyalty programs at the same time, and each loyalty program can include many customers. To keep a single-valued surrogate key in the Customer dimension while still allowing reports to filter sales by loyalty program, which structured data element should the data architect add between the two dimensions?
Create a junk dimension that combines loyalty program codes with other flags.
Convert the Customer dimension to a Type 2 slowly changing dimension.
Store the loyalty program ID as a degenerate dimension in the fact table.
Introduce a bridge table that lists every valid customer-loyalty program pair.
When two dimension entities (Customer and Loyalty Program) have a many-to-many relationship, introducing a bridge table-sometimes called a helper or association table-breaks the relationship into two one-to-many joins. The bridge table stores only the surrogate keys (and any optional weighting columns) for each valid customer-program pair. This preserves the single-valued Customer key in the fact table and lets analysts slice measures by loyalty program without double counting. A slowly changing dimension addresses historical attribute changes, a junk dimension bundles unrelated low-cardinality flags, and a degenerate dimension stores identifiers directly in the fact table; none of these resolve a many-to-many relationship between two full dimensions.
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CompTIA Data+ DA0-002 (V2)
Data Concepts and Environments
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