Surrogate Primary Keys
- Computer Science Department
A surrogate key is a primary key created by the database designer to simplify the identification of entity instances
One advantage of a surrogate key is that because it has no intrinsic meaning, values for it can be generated by the DBMS to ensure that unique values are always provided
Surrogate keys are useful in the following situations:
When there is no natural key
When the selected candidate key has embedded semantic contents
When the selected candidate key is too long
Surrogate keys are used instead of natural keys, which are based on existing data in a table, because they provide a reliable and consistent means of uniquely identifying each record. They also have the advantage of being immune to changes in the underlying data, such as if a natural key were to change or become duplicated.
One common example of a surrogate key is an auto-incrementing ID field. As each new record is added to a table, the database management system automatically assigns a unique ID to the record. This ID becomes the primary key for the table, and it is used to refer to the record in other tables that have relationships with it.
While surrogate keys do not have any inherent business meaning, they are widely used in database design because they provide a simple and reliable way to uniquely identify records. They also allow for efficient indexing and searching of large data sets.