Reviewed by Aditya Kumar · Last reviewed 2026-03-24
SCD types: 1—overwrite (no history); 2—add row (full history); 3—add column (previous value). Type 4—separate history table. Type 5—mini-dimension. Type 6—hybrid. Use 1 for corrections; 2 for audit/history; 3 for single previous value. Type 2 most common in DW. **Why it...
SCD types: 1—overwrite (no history); 2—add row (full history); 3—add column (previous value). Type 4—separate history table. Type 5—mini-dimension. Type 6—hybrid. Use 1 for corrections; 2 for audit/history; 3 for single previous value. Type 2 most common in DW. 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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