Slowly Changing Dimensions – Type 2

Slowly Changing Dimensions – Type 2




 Updates the dimension table and keeps track of the old values through using "EffectiveDate" and "ExpirationDate" fields, while each date has its own record in the dimension table and a foreign key in the fact table.
  • These changes involve the creation of a fresh version of the dimension entity in the form of a new row.
  • Typically, a bit column in the dimension table is used as a flag to indicate which version of the dimension row is the current one.
  • Additionally, DateTime columns are often used to indicate the start and end of the period for which a version of the row was (or is) current.Maintaining start and end dates makes it easier to assign the appropriate foreign key value to fact rows as they are loaded so they are related to the version of the dimension entity that was current at the time the fact occurred.

 Note: 
Each row in a dimension table represents an instance of a business entity by which the measures in the fact table can be aggregated


References:
https://www.slideshare.net/antoniosch/building-data-warehouse-in-sql-server?from_action=save

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