Surrogate Keys

Definition

Surrogate keys are unique identifiers used in databases to distinguish records, which are not derived from application data. They serve as a substitute for natural keys and are often utilized in data warehousing to enhance the handling of slowly changing dimensions and maintain conformed dimensions. By using surrogate keys, data models can effectively manage changes in attribute values over time without affecting the relationships and integrity of the underlying data.

5 Must Know Facts For Your Next Test

1. Surrogate keys are usually generated automatically by the database system, often as sequential numbers or GUIDs (Globally Unique Identifiers).
2. They help avoid issues with natural keys, such as changes in business logic or format, which can complicate data integrity.
3. Using surrogate keys simplifies the process of managing slowly changing dimensions by allowing easy tracking of historical changes without disrupting existing relationships.
4. Surrogate keys can improve query performance, especially in large datasets, since they are typically smaller and more efficient than natural keys.
5. They are essential for maintaining conformed dimensions across different fact tables within a data warehouse.

Review Questions

• How do surrogate keys facilitate the management of slowly changing dimensions in a data warehouse?
  • Surrogate keys help manage slowly changing dimensions by providing a stable and consistent identifier for each record, regardless of changes in attribute values. When an attribute in a dimension changes, instead of altering the existing record, a new record can be created with a new surrogate key. This approach allows for maintaining historical accuracy while keeping the original data intact, thus simplifying the tracking of changes over time.
• In what ways do surrogate keys differ from natural keys, and why might an organization choose to use one over the other?
  • Surrogate keys differ from natural keys primarily in that they are not derived from existing business data but are generated uniquely by the system. Organizations may choose surrogate keys to avoid issues related to changes in natural key values due to business requirements or data format changes. Additionally, surrogate keys tend to be smaller and more efficient for indexing and querying purposes, making them preferable in large-scale databases.
• Evaluate how the use of surrogate keys impacts the overall integrity and performance of a data warehouse.
  • The use of surrogate keys significantly enhances both integrity and performance in a data warehouse setting. By providing a consistent identifier that is independent of the business logic, surrogate keys ensure that relationships between records remain stable even as underlying data changes. This stability aids in maintaining accurate historical records and reduces complexity when handling slowly changing dimensions. Performance-wise, surrogate keys streamline queries due to their typically smaller size compared to natural keys, enabling faster access to data across large datasets.

Related terms

Natural Key: A natural key is a type of primary key that is formed from attributes that already exist in the real world and have business meaning.

Primary Key: A primary key is a unique identifier for a record in a database table, ensuring that each record can be uniquely retrieved.

Slowly Changing Dimension (SCD): Slowly Changing Dimensions are dimensions in data warehousing that change slowly over time, allowing for the tracking of historical data.