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A surrogate key (or synthetic key, pseudokey, entity identifier, factless key, or technical key [citation needed]) in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data, unlike a natural (or business) key. [1]
In the data warehouse practice of extract, transform, load (ETL), an early fact or early-arriving fact, [1] also known as late-arriving dimension or late-arriving data, [2] denotes the detection of a dimensional natural key during fact table source loading, prior to the assignment of a corresponding primary key or surrogate key in the dimension table.
Having a Type 2 surrogate key for each time slice can cause problems if the dimension is subject to change. [1] A pure Type 6 implementation does not use this, but uses a surrogate key for each master data item (e.g. each unique supplier has a single surrogate key). This avoids any changes in the master data having an impact on the existing ...
The fact table also contains foreign keys from the dimension tables, where time series (e.g. dates) and other dimensions (e.g. store location, salesperson, product) are stored. All foreign keys between fact and dimension tables should be surrogate keys, not reused keys from operational data.
Although surrogate key use places a burden on the ETL system, pipeline processing can be improved, and ETL tools have built-in improved surrogate key processing. The goal of a dimension table is to create standardized, conformed dimensions that can be shared across the enterprise's data warehouse environment, and enable joining to multiple fact ...
Surrogate: An artificial key made from data that is system assigned or generated when another candidate key exists. Surrogate keys are usually numeric ID values and often used for performance reasons. [citation needed] Candidate A key that may become the primary key. Primary The key that is selected as the primary key.
A key that has an external, real-world meaning (such as a person's name, a book's ISBN, or a car's serial number) is sometimes called a "natural" key. If no natural key is suitable (think of the many people named Brown), an arbitrary or surrogate key can be assigned (such as by giving employees ID numbers). In practice, most databases have both ...
Referential integrity is a property of data stating that all its references are valid. In the context of relational databases , it requires that if a value of one attribute (column) of a relation (table) references a value of another attribute (either in the same or a different relation), then the referenced value must exist.