Surrogate key is the key that can be substituted with the primary key. It is a unique key that uniquely identifies the each row that is used. This also allows the unique search of the primary key to the table. It is used in the database to uniquely identify an entity in a model or an object that is present in the database. This key is not derived from any of the data entity and not even from the application data. These are represented either in the form of numbers or integers. This kind of keys is generated from the system and it is not at all visible to the outside world. This key can be used as a primary key for a given database and there are few differences between primary key and surrogate key. There remains many to one relationship between primary and surrogate keys.