Establishing Keys for Each Table
Your next task is to establish keys for each table in the database. There are four main types of keys: candidate, primary, foreign, and non-keys. A key's type determines its function within the table.
The first type of key you establish for a table is the candidate key, which is a field or set of fields that uniquely identifies a single instance of the table's subject. Each table must have at least one candidate key. You'll eventually examine the table's pool of available candidate keys and designate one of them as the official primary key for the table.
Before you can designate a field as a candidate key, you must make certain it complies with all of the Elements of a Candidate Key. These ...