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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Definition

Types of Data Warehouse Dimension

by Amol 18. February 2011 08:51

In a data warehouse, dimension is one of the perspectives that can be used to analyze the data in an OLAP cube.
When you are browsing the data in a cube, you can view the data from the perspective of different combinations of dimensions.

With dimension, data can be slice and dice to analyse it in different prospective. Dimensions are used to provide structured lebeling information to measures. Another use of dimension other than lebeling is to provide filtering, grouping.

For example, for a Sales database, the dimensions could include Product, Time, Store, and Promotion.

Each dimension may have one or more hierarchies applied to it. For the "Date" dimension, there are several possible hierarchies: "Day > Month > Year", "Day > Week > Year", "Day > Month > Quarter > Year", etc.

Types of dimension :

  1. Conformed dimension
  2. Junk dimension
  3. Degenerate dimension
  4. Role-playing dimensions

 

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