Following are the different types of dimension tables in the context of data warehousing:-

• Slowly CHANGING Dimensions (SCD): Slowly changing dimensions are dimension attributes that tend to vary slowly over time RATHER than at a regular period of time. For example, the address and phone number may change, but not on a regular basis. Consider the case of a man who travels to several nations and must change his address according to the place he is visiting. This can be accomplished in ONE of three ways:
  • Type 1: Replaces the value that was PREVIOUSLY entered. This strategy is simple to implement and aids in the reduction of costs by saving space. However, in this circumstance, history is lost.
  • Type 2: Insert a new row containing the new value. This method saves the history and allows it to be accessed at any time. However, it takes up a lot of space, which raises the price.
  • Type 3: Add a new column to the table. It is the ideal strategy because history can be easily preserved.
• Junk Dimension: A trash dimension is a collection of low-cardinality attributes. It contains a number of varied or disparate features that are unrelated to one another. These can be used to implement RCD (rapidly changing dimension) features like flags and weights, among other things.
• Conformed Dimension: Multiple subject areas or data marts share this dimension. It can be utilised in a variety of projects without requiring any changes. This is used to keep things in order. Dimensions that are exactly the same as or a proper subset of any other dimension are known as conformed dimensions.
• Roleplay Dimension: Role-play dimension refers to the dimension table that has many relationships with the fact table. In other words, it occurs when the same dimension key and all of its associated attributes are linked to a large number of foreign keys in the fact table. Within the same database, it might serve several roles.
• Degenerate Dimension: Degenerate dimension attributes are those that are contained in the fact table itself rather than in a separate dimension table. For instance, a ticket number, an invoice number, a transaction number, and so on.