Degenerate Dimensions in the Fact Table

Concepts covered: dmFactTables

Your degenerate dimension answer: 'A degenerate dimension stays in the fact table. No separate table. No surrogate key. invoice_number is unique per row with no additional attributes worth storing. Creating dim_invoice with one column and a surrogate key doubles storage for zero analytical benefit.' The key phrase is 'zero analytical benefit.' That is the Kimball justification for degeneration. The Decision: Which Attributes Stay on the Fact Table State the rule: 'If the attribute is unique per fact row and has no additional columns that would join to it, it is degenerate. A one-to-one dimension with the same cardinality as the fact table provides no analytical value.' Name the anti-pattern: 'one-to-one dimension.' The interviewer rarely hears candidates name it. The Interview Trap Some in

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