Dimensional Modeling Concepts to Learn

To understand Dimensional Modeling ,
Following concepts are very very important

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• Basic dimensional modeling concepts
• Conformed dimensions
• Slowly changing dimensions
• Additional concepts in dimensional modeling
-Hierarchies and snowflaking
-Degenerate and junk dimensions
-Many to many dimensions
• The dimensional modeling process

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• Populating dimension tables
-Using the slowly changing dimension wizard
-Avoiding the slowly changing dimension wizard

• Populating fact tables
-Basic fact table processing
-The surrogate key pipeline
-Advanced issues in fact table processing

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Types of Dimensions

Dimensions are of 3 types mainly in case of slowly changing dimensions:

Type 1 ->Doesnt maintain any history and is update only.

Type 2-> Maintains full history.Insert row when certain attributes change else update row.The latest record is identified by a flag or date field which is called the MRI or Most Recent Indicator

Type 3->Maintains partial history.History is maintained as columns and not rows.Hence it is predecided as to till how many levels of history you want to maintain.

There are three types of Dimesions

Confirmed Dimensios, Junk Dimesions, Degenerative Dimesions

Comfirmed is some thing which can be shared by shared by multiple Fact Tables or multiple Data Marts.

Junk Dimensiions is grouping flagged values

Degenerative Dimension is something dimensional in nature but exist fact table.