CHAPTER 7 What are keys?
More than one John DoeWhich is the right Customer?Recall by the key
There is a lot of data out there, but how do you sift through it all to find what you’re looking for? That’s where keys come in. A key is one or more attributes whose purposes include enforcing rules, efficiently retrieving data, and allowing navigation from one entity to another. This chapter defines keys and distinguishes between the terms candidate, primary, and alternate keys. Surrogate keys and foreign keys and their importance are also explained.
Candidate Key (Primary and Alternate) Explained
A candidate key is one or more attributes that uniquely identify an entity instance. An ISBN (International Standard Book Number) is assigned to every title. ...