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Explain Slowly Changing Dimensions (SCD) and its types

SQLeasy0.4 min readPremium
Frequency
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Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
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1,863
across 7 categories
Asked at these companies
JIO
Expert AnswerPremium
81 wordsInterview-ready
**Architectural Logic**: SCD tracks dimension attribute changes; type choice affects history and storage. **Type 1**: Overwrite; no history. **Type 2**: New row; effective dates; current flag; full history. **Type 3**: Previous value column; limited history. **Type 4**: History table. **Type 6**: Hybrid (1+2+3). **Most Common**: Type 2 for customer, product dimensions. **Implementation**: MERGE or INSERT/UPDATE; change detection via hash. **Scalability**: Type 2 row growth; surrogate keys....
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