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Discuss strategies for handling schema evolution in data warehouses.

SQLmedium0.3 min read

**Architectural Logic**: Schema evolution must preserve compatibility and enable safe rollout. **Strategies**: (1) Additive only—add columns with defaults; avoid drops/renames. (2) Schema registry—version schemas; validate on read. (3) Backfill—populate new columns for...

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Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Disney+ Hotstar
Key Concepts Tested
window

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Expert Answer
70 words

Architectural Logic: Schema evolution must preserve compatibility and enable safe rollout. Strategies: (1) Additive only—add columns with defaults; avoid drops/renames. (2) Schema registry—version schemas; validate on read. (3) Backfill—populate new columns for historical. (4) Multiple versions—support old and new during transition; deprecate. (5) Schema-on-read—struct/variant for flexible. (6) dbt—version models; run migrations. Why Additive: Non-additive changes break downstream. Scalability: Compatibility windows; test migrations. Cost: Backfill can be expensive; plan for incremental.

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