Slowly Changing Dimensions | Data Warehousing

Type 1 Slowly Changing Dimension

Type 1 SCD is often called an ‘in-place’ ETL pattern. It is the simplest SCD, but only works for certain use-cases. While it replaces the old value with the new, it does not maintain any history.

Type 2 Slowly Changing Dimension

Type 2 SCD is referenced as the ‘as-is’ pattern. This is because registering a change adds a completely new dimension table row while leaving the existing row as-is. If Type 1 is ‘too hot’ in the Goldilocks metaphor, Type 2 is ‘too cold.’

Type 3 Slowly Changing Dimension

Type 3 SCD creates multiple versions of history within your dimension tables. Where Type 2 added a new row to row to reflect a change, Type 3 adds a new column.

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