Wednesday, March 13, 2013

What are Fast Changing Dimensions?

Fast Changing Dimensions are dimensions that keep changing rapidly. Previously we had discussed about slowly changing dimension, which can be handled by Type1,Type2 or Type3.In case of rapidly changing dimension it cannot be managed by any of these Types.

For RAPIDLY CHANGING DIMENSION we need to split the actual dimension table into many Mini Dimensions. These Mini dimensions can be one ore more and will contain the Fast Changing attributes in the dimensions So now there will be one or more mini dimensions and primary dimension table. Also the fact table will have two or more foreign keys, one for the primary dimension table and another for the one or more mini-dimensions.

Hence we will have two dimensions now,
  1.  One table is the actual dimension minus the fast changing attributes.
  2.  Another is the mini dimensions having the fast changing attributes.

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