Role-playing dimension

by Amol 19. February 2011 11:15

 

Role-playing dimension:

Dimensions are often recycled for multiple applications within the same database. For instance, a "Date" dimension can be used for "Date of Order", as well as "Date of Delivery", or "Start Date, End Date. these dimensions are called as a "role-playing dimension".

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Degenerate Dimension

by Amol 19. February 2011 11:12

 

Degenerate Dimension:

Degenerate Dimension is a dimension which is derived from the fact table and doesn't have its own dimension table.

Degenerate Dimension can be described in other words as

  • A degenerate dimension is data that is dimensional in nature but stored in a fact table.
  • Any Dimension keys that are not joined to dimension table are considered as degenerate dimension.
  • Degeneratate dimension when dimension keys are part fact table without having dimension.

For examle :

Order Number, Receipt Number, Bill Number are the degenerate dimension as they are part of trasaction fact table without having dimension attached to it.

 

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Definition

Junk dimension

by Amol 19. February 2011 11:09

 

Junk dimension:

Junk dimension is group of flags which gives us kind of Yes / No or True / False answer. The attributes in junk dimension do not belong to the fact table. Junk dimension contains a unique key to all possible combinations of flags and the generated unique key is used in fact table. 
Junk dimensions are also used for placing attributes like non-generic comments from the fact table. Such attributes might consist of data from an optional comment field when a customer places an order.

 

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