How many types of dimensions?

They are 4 types of dimensions:

• Conformed dimension
• Junk dimension
• Degenerate attribute
• Role-playing dimension   

Conformed dimension:

It is the dimension which is sharable across the multiple facts or data model. This is also called as Role Playing Dimensions.

Junk dimension:

A number of very small dimensions might be lumped (a small irregularly shaped) together to form a single dimension, a junk dimension – the attributes are not closely related. Grouping of Random flags and text attributes in a dimension and moving them to a separate sub dimension is known as junk dimension.

Degenerated dimension:

In this degenerate dimension contains their values in fact table and the dimension id not available in dimension table. Degenerated Dimension is a dimension key without corresponding dimension.

Role-playing dimension:

Dimensions which are often used for multiple purposes within the same database are called role-playing dimensions. For example, a date dimension can be used for “date of sale", as well as "date of delivery", or "date of hire".