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What is a “surrogate key”?
A surrogate key is a term used in the field of database management to refer to a virtual or artificial key that is used to generate primary keys for database tables. This key is typically unrelated to the actual data being stored and is instead created solely for the purpose of uniquely identifying each record in a table.
Why are surrogate keys used?
Surrogate keys are used in situations where it might be challenging or impractical to use natural keys to uniquely identify records in a table. Natural keys are keys that are derived from the actual data stored in a table, such as employee IDs, product codes, or social security numbers. While using natural keys might seem logical, they can present certain limitations and complications.
One of the main reasons for using surrogate keys is to maintain data integrity. Surrogate keys are often implemented as auto-incrementing integers, ensuring that each new record inserted into a table is assigned a unique identifier. This eliminates the possibility of duplicate or conflicting keys, which can occur when using natural keys.
Another advantage of surrogate keys is that they provide abstraction and independence from the actual data. This means that even if the natural key values change, the surrogate key remains constant. This can be useful in scenarios where the underlying data might be subject to updates or modifications.
How are surrogate keys implemented?
There are different methods for implementing surrogate keys, but one common approach is to use an auto-incrementing integer as the surrogate key. In most database management systems, there are built-in mechanisms to generate these auto-incrementing values automatically. This means that when a new record is inserted into a table, the surrogate key is automatically assigned the next available value.
In addition to auto-incrementing integers, other types of surrogate keys include globally unique identifiers (GUIDs), which are strings of alphanumeric characters that have an extremely low probability of collision.
Surrogate keys are typically implemented by adding an additional column to a table, specifically to serve as the surrogate key. This column is given a consistent data type, such as an integer or string, to ensure compatibility with the database system.
Conclusion
In summary, a surrogate key is a virtual or artificial key used to generate primary keys in database tables. Surrogate keys are used to overcome challenges associated with using natural keys and provide benefits such as data integrity and abstraction. They are implemented using auto-incrementing integers or other unique identifier mechanisms. By understanding the concept of surrogate keys, database administrators can design efficient and robust database systems.
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