A dimension is something that qualifies the quantity or measures. Dimensions store the textual descriptions of the business. With help of dimension you can easily identify the measures.The different types of dimension tables are available as below:
Read:
- Types of Fact Tables in a Data Warehouse
- Data Warehouse Fact Constellation Schema and Design
- Data Warehouse Three-tier Architecture in Details
Types of Dimension Tables in a Data Warehouse
Below are the commonly used dimension tables in data warehouse:
Conformed Dimension
A conformed dimension is the dimension that is shared across multiple data mart or subject area. Company may use the same dimension table across different projects without making any changes to the dimension tables.
Conformed dimension example would be Customer dimension, i.e. both marketing and sales department can use Customer dimension for their reporting purpose.
Junk Dimension
A junk dimension is a grouping of typically low cardinality attributes, so you can remove them from main dimension.
You can use Junk dimensions to implement the rapidly changing dimension where you can use it to stores the attribute that changes rapidly.
For example, attributes such as flags, weights, BMI (body mass index) etc
Degenerated Dimension
A degenerated dimension is a dimension that is derived from fact table and does not have its own dimension table.
For example, receipt number does not have dimension table associated with it. Such details are just for information purpose.
Role Playing Dimension
Dimensions which are often used for multiple purposes within the same database are called role-playing dimensions.
For example, you can use a date dimension for “date of sale”, as well as “date of delivery”, or “date of hire”.
Based on the frequency of data change below are the types of Dimension Tables:
Unchanging or static dimension (UCD)
Dimensions values are static and will not change
Slowly changing dimension (SCD)
Attribute values changes slowly over time. Based on the frequency of data change and history preservation, there are various slowly changing dimensions available.
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Rapidly changing Dimension (RCD)
Attribute values changes rapidly