**A primary key that serves no other purpose.** In the case a relational database table contains no single "best" [[Primary Key]] (or even no single _possible_ Primary Key), a new field is added whose **only purpose is to uniquely identify a row**. These fields are often named "ID" or something to that effect. Fields whose only purpose in a table is to allow each row to be uniquely identified are called "Surrogate Keys". Surrogate keys are necessary to prevent a collisions stemming from coincidence. For example: you have a student ID because your name is Joshua Brown and there's another "Joshua Brown" in your class. Surrogate keys may often just be more convenient. You could concoct a crazy combination of fields that could, in aggregate, be called a primary key... but it's just easier to add an "ID" column and call it good. # Examples - Social Security Numbers - Student # or Employee # - Account numbers - [[UUID]]s - Row numbers **** # More ## Sources [Primary key](https://en.wikipedia.org/wiki/Primary_key) ## Related - [[Primary Key]] - [[Relational Databases]]