Designing Fact Tables for Correct Aggregation

The strongest closing move in an additive measures interview is showing you design fact tables that make incorrect aggregation impossible. Not 'document the rules' but 'store only additive components so there is no way to get it wrong.' This is the difference between a schema that works when people follow the rules and a schema that works regardless. The Checklist You Walk Through in the Interview A Complete Example The table comment IS the documentation. Putting grain and additivity rules in the table comment means every engineer who reads the schema gets the rules. This is a senior production practice that interviewers notice. Vocabulary That Signals Seniority The Bridge Move Your closing move: 'The fact table stores components. The metrics layer defines the formulas. This separation gua