Different types of SCDs

Slowly Changing Dimensions (SCDs) are methods used in data warehousing to manage and track changes in dimension data over time. There are several types of SCDs, each handling changes in different ways:

• Type 0 – Fixed Dimension: No changes allowed. The historical data is preserved as it is¹.
• Type 1 – No History: The new data overwrites the old data. No history is kept¹².
• Type 2 – Row Versioning: Each change creates a new record with a version or timestamp. This maintains full history².
• Type 3 – Previous Value Column: Adds a new column to store the previous value of the changed data².
• Type 4 – History Table: Uses a separate history table to track changes².
• Type 6 – Hybrid: Combines aspects of Types 1, 2, and 3 to track changes².

Each type has its use cases depending on the business requirements and how the historical data should be preserved and analyzed.

Source: Conversation with Bing, 5/14/2024
(1) Slowly Changing Dimensions (SCD): 4 Types & How to Implement – ThoughtSpot. https://www.thoughtspot.com/data-trends/data-modeling/slowly-changing-dimensions-in-data-warehouse.
(2) Slowly Changing Dimensions: 5 Key Types and Examples – Hevo Data. https://hevodata.com/learn/slowly-changing-dimensions/.
(3) Mastering Slowly Changing Dimensions (SCD) | DataCamp. https://www.datacamp.com/tutorial/mastering-slowly-changing-dimensions-scd.