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What are Slowly Changing Dimensions (SCD Type 1 vs Type 2 vs Type 3) in data warehouses?

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Edited by Rahul Sharma · Aug 24, 2026 6:25 AM

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What are Slowly Changing Dimensions (SCD Type 1 vs Type 2 vs Type 3) in data warehouses?

Summary snapshot
Managing historical record changes over time using `effective_date` and `is_current` columns.
Content snapshot
### SCD Strategy - **SCD Type 1**: Overwrites legacy records (no history). - **SCD Type 2**: Inserts new row record with start/end date bounds (full historic audit trail). - **SCD Type 3**: Adds a `previous_val` column (limited history).
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https://developers.google.com/search/docs

Version 1 (Original Post)

Published by Rahul Sharma · Aug 9, 2026 5:37 AM

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Original Title

What are Slowly Changing Dimensions (SCD Type 1 vs Type 2 vs Type 3) in data warehouses?

Original Summary
Managing historical record changes over time using `effective_date` and `is_current` columns.
Original Content
### SCD Strategy - **SCD Type 1**: Overwrites legacy records (no history). - **SCD Type 2**: Inserts new row record with start/end date bounds (full historic audit trail). - **SCD Type 3**: Adds a `previous_val` column (limited history).
Original Sources

https://developers.google.com/search/docs