Wednesday, September 26, 2007

Slowly Changing Dimension (SCD)

There are three common SCD types:

  • Type 0 (fixed): when an attribute of a dimension is fixed attribute, it cannot be changed.
  • Type 1 (changing): This technique that is also known as Restating History indicates that the changes in the attribute must be replaced.
  • Type 2 (historical): This type of SCD that is known as historical attribute is used for attribute which changes over time. Furthermore, it is important for us to keep the changes and reflect them in the reports.

If you have a historical dimension, and it changes a lot over a specific time, and the changes are not important, you can change the dimensions attribute type to type 1 and do your changes, then change the type of it after it stabilized.

You can find more information in wikipedia.

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