In Clarity, how do SCD Type I and Type II differ?

In Clarity, how do SCD Type I and Type II differ?

• A. Type I overwrites old values; Type II creates new version rows with effective dates
• B. Type I preserves history; Type II overwrites
• C. Type I is about deletion; Type II about insertion
• D. Type I uses surrogate keys; Type II uses natural keys

Answer: (A)

SCD in Clarity focuses on how changes to a dimension’s attributes are stored over time, specifically whether history is kept or overwritten. Type I updates replace the existing value in place, so the old value is lost and there’s no historical record of what the value used to be. Type II preserves history by creating a new row for the updated version, typically with an effective date (and sometimes an end date), so you can query the data as it existed at any point in time. This is why the best description is that Type I overwrites old values, while Type II creates new version rows with effective dates. The other statements mix up these behaviors: Type I does not preserve history, Type II does not simply overwrite, and the distinction isn’t about deletion vs insertion or about surrogate vs natural keys.

SCD in Clarity focuses on how changes to a dimension’s attributes are stored over time, specifically whether history is kept or overwritten.

Type I updates replace the existing value in place, so the old value is lost and there’s no historical record of what the value used to be.

Type II preserves history by creating a new row for the updated version, typically with an effective date (and sometimes an end date), so you can query the data as it existed at any point in time. This is why the best description is that Type I overwrites old values, while Type II creates new version rows with effective dates.

The other statements mix up these behaviors: Type I does not preserve history, Type II does not simply overwrite, and the distinction isn’t about deletion vs insertion or about surrogate vs natural keys.