Reviewed by Aditya Kumar · Last reviewed 2026-03-24
1NF: atomic values, no repeating groups. 2NF: 1NF + no partial dependencies (all non-key attributes depend on full key). 3NF: 2NF + no transitive dependencies (non-key depends only on key). Example: Orders(order_id, customer_id, customer_name) violates 3NF—customer_name depends...
1NF: atomic values, no repeating groups. 2NF: 1NF + no partial dependencies (all non-key attributes depend on full key). 3NF: 2NF + no transitive dependencies (non-key depends only on key). Example: Orders(order_id, customer_id, customer_name) violates 3NF—customer_name depends on customer_id; split to Orders, Customers. BCNF: every determinant is candidate key. Why it matters: Design choices compound at scale—wrong approach can cause 100× overhead. Scalability trade-offs: Profile before optimizing; validate on sample then full. Cost implications: Suboptimal choices multiply at billion-row scale.
Red Flag: Generic textbook answers. Pro-Move: 'At scale we measured X, implemented Y, achieved Z%—validated and iterated.'
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