"Slowly Changing Dimensions" is the category of dimensions that change over t…

"Slowly Changing Dimensions" is the category of dimensions that change over time in a fact + dimension/star schema architecture. Data engineers must consider how to handle these dimensions in a way that tracks them over time.

There are 6 types popularized by Ralph Kimball.

1. Retain original (immutable)
2. Overwrite (no history)
3. Add new row (infinite history, but space inefficient and costly)
4. Add new attribute (ie. original_supplier or previous_supplier)
5. Add history table
6. "outrigger"
7. Unpredictable Changes with Single-Version Overlay

https://en.wikipedia.org/wiki/Slowly_changing_dimension