SCD Type 3

Definition

SCD Type 3, or Slowly Changing Dimension Type 3, is a method used in data warehousing to manage changes in dimensional data by storing the current and previous values of an attribute. This approach allows organizations to track historical changes while also enabling quick access to the most recent information. It is particularly useful when businesses need to understand how a specific attribute has changed over time without requiring extensive historical tracking.

5 Must Know Facts For Your Next Test

1. SCD Type 3 typically involves adding additional columns to the dimension table for both the current and prior values of an attribute.
2. This approach is best suited for scenarios where only a limited number of changes are expected for a particular attribute over time.
3. SCD Type 3 can help streamline reporting by keeping the most relevant data easily accessible while still retaining some level of historical context.
4. Unlike SCD Type 2, which can create significant table growth, SCD Type 3 maintains a smaller footprint by limiting the number of records created.
5. Using SCD Type 3 can simplify querying for certain types of analysis, as it provides both the current and previous states of an attribute within the same record.

Review Questions

• How does SCD Type 3 differ from other types of Slowly Changing Dimensions in terms of data storage and historical tracking?
  • SCD Type 3 differs from other Slowly Changing Dimensions by storing both current and previous values of an attribute within the same record, typically through additional columns. In contrast, SCD Type 1 overwrites existing values with new ones, losing all history, while SCD Type 2 creates separate records for every change, preserving complete historical data. This makes SCD Type 3 a middle-ground solution that balances some historical tracking with efficient data storage.
• What are the advantages of using SCD Type 3 over SCD Type 2 in a data warehousing context?
  • The advantages of using SCD Type 3 over SCD Type 2 include a reduced storage requirement and simplified querying. Since SCD Type 3 retains only the current and one prior value rather than an entire history, it results in less table growth and easier management. Additionally, queries can be more straightforward since both values are readily available within the same record, making it quicker for analysts to access relevant data without needing complex joins.
• Evaluate the scenarios where implementing SCD Type 3 would be more beneficial than other methods, considering business needs and data characteristics.
  • Implementing SCD Type 3 is particularly beneficial in scenarios where an organization anticipates infrequent changes to specific attributes but still needs to capture limited historical context. For example, if a business tracks customer account statuses that only change occasionally but require easy access to both current and last status, SCD Type 3 would be ideal. This method avoids the overhead associated with constant record creation found in SCD Type 2, making it suitable for environments focused on efficiency while still allowing some degree of historical analysis.

Related terms

Slowly Changing Dimension (SCD): A data management concept that refers to the way dimensions in a database change slowly over time, necessitating different strategies for handling these changes.

SCD Type 1: A method where changes to dimensional data overwrite the existing values, resulting in no history being preserved.

SCD Type 2: A technique that captures all historical changes by creating new records in the dimension table for each change, allowing full historical tracking.