A surrogate key is basically an identifier that uniquely identifies modeled entities or objects in a database. Not being derived from any other data in the database, surrogate keys may or may not be used as primary keys. It is basically a unique sequential number. If an entity exists in the outside world and modeled within the database, or represents an object within the database, it is denoted by a surrogate key. In these cases, surrogate keys for specific objects or modeled entities are generated internally.
