Are you unsure whether you should use a surrogate identifier or a natural value for a primary key? Check out Michelle A. Poolet’s article “Surrogate Key vs. Natural Key.” In this article, Michelle discusses the differences between the two types of keys and explains how to choose a primary key, with a focus on the four criteria a natural key or a surrogate key must meet before they’re chosen as the primary key and the key factors that you should consider before choosing a primary key.

For more information about primary keys, see 

SQL by Design: How to Choose a Primary Key 
What Makes a Good Primary Key?