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Describe how you would implement Slowly Changing Dimensions (SCD) in an ETL workflow.

SQLeasy0.5 min readPremium
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
BCG
Key Concepts Tested
etl
Expert AnswerPremium
99 wordsInterview-ready
**Architectural Logic**: SCD implementation depends on type; MERGE is the workhorse for atomicity. **SCD1**: UPDATE dim SET col = new_val WHERE key = X. **SCD2**: INSERT new row with effective_from; UPDATE current row's effective_to; set current_flag. **SCD3**: Add prev_col; on change, shift current→prev. **ETL Flow**: (1) Extract changed records. (2) Lookup dimension. (3) Apply SCD logic (MERGE or INSERT/UPDATE). (4) Generate surrogate keys....
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