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Data & Analytics · Intermediate

Slowly Changing Dimension (SCD)

Techniques for handling changes to dimension attributes over time, such as a customer moving city.

Definition

Common types are Type 0 (retain original), Type 1 (overwrite), Type 2 (add a new row with effective dates to keep history), Type 3 (add a 'previous value' column) and hybrids such as Type 6. The choice depends on whether history must be reported.

Exam tip

History required = Type 2; history not needed = Type 1; only the prior value needed = Type 3.

Related terms