Track · 5:09 · Liner note

Slowly Changing Dimensions

Name: Slowly Changing Dimensions
Duration: 5 min 9 s
Description: Slowly changing dimensions (SCD) are techniques for tracking how dimension attributes, such as a customer's address or segment, change over time, for example by overwriting the value or keeping a new row for each version.

Slowly changing dimensions (SCD) are techniques for tracking how dimension attributes, such as a customer's address or segment, change over time, for example by overwriting the value or keeping a new row for each version.

A customer moves cities. Last year’s sales belong to the old region, this year’s to the new one, and your report has to know which is which. Slowly Changing Dimensions is the family of techniques that answers it: overwrite the value, add a new row with validity dates, or keep previous values alongside.

There is no universally right type. The choice depends on whether history matters for the question being asked. Decide per attribute, document the choice and test with a record that has changed twice.