Chapter 2, Problem 2PE

Program Plan Intro

Primary Key:

• A primary key is a special column of a relation used for uniquely identifying a relation.
• The primary key can be one column or combination of columns. The primary key will uniquely identify all the records of a table.
• The features of a primary are:
  • The primary key contains a unique value for each row of data.
  • The primary key column cannot contain null values.

Foreign key:

• A foreign key is an attribute/column which is used for establishing relationship between two tables/relations.
• A foreign key must be primary key of the table to which it is referring.