In data warehousing, surrogate keys are artificially created keys that uniquely identify each record in a dimension table. They are used as a substitute for natural keys, which are keys derived from the source data. Here's a breakdown of the concept:
What are Surrogate Keys?
- A surrogate key is a unique identifier, typically a numeric value, that is generated specifically for the data warehouse.
- It has no inherent business meaning and is solely used for technical purposes.
- They are generated during the ETL (Extract, Transform, Load) process.
Why Use Surrogate Keys?
- Stability:
- Natural keys can change over time, which can cause problems in a data warehouse. Surrogate keys remain constant, ensuring data integrity.
- Independence:
- Surrogate keys decouple the data warehouse from the source systems. This means that changes in the source systems will not affect the data warehouse structure.
- Performance:
- Numeric surrogate keys are typically smaller and faster to process than complex natural keys, which improves query performance.
- Handling SCDs:
- Surrogate keys are essential for implementing Slowly Changing Dimensions (SCDs), particularly SCD Type 2, where new records are created to track historical changes.
- Data Integration:
- When integrating data from multiple source systems, surrogate keys help to resolve conflicts that may arise from overlapping or inconsistent natural keys.
- Anonymization:
- They can be used to remove personally identifiable information from a database.
Key Characteristics:
- Unique: Each record has a unique surrogate key.
- Meaningless: They have no business meaning.
- Stable: They do not change over time.
- Simple: They are typically numeric values.
