Determine keys for tables

The columns of a table are either key columns or descriptor columns. A key column is one that uniquely identifies a particular row in the table. For example, a social security number is unique for each employee. A descriptor column specifies the nonunique characteristics of a particular row in the table. For example, two employees can have the same first name, Sue. The first name Sue is a nonunique characteristic of an employee. The main types of keys in a table are primary keys and foreign keys.

You designate primary and foreign keys when you create your tables. Primary and foreign keys are used to relate tables physically. Your next task is to specify a primary key for each table. That is, you must identify some quantifiable characteristic of the table that distinguishes each row from every other row.