Science Fair Project Encyclopedia
A surrogate key is frequently a sequential number (e.g., a Sybase "identity column") but doesn't have to be. Having the key independent of all other columns insulates the database relationships from changes in data values or database design (making your database more agile) and guarantees uniqueness.
Some database designers use surrogate keys religiously regardless of the suitability of other candidate keys. However, other database designers will use a key already present in the data, if there is one: the addition of a surrogate key will slow down access to the table, particularly if it is indexed.
"Surrogate key" may also be known as "System-generated key", "Database Sequence number", or an "Arbitrary, unique identifier".
Some other options for surrogate keys are:
See also: Intelligent key
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details