Chapter 3, Problem 10P

Program Plan Intro

Primary Key:

A primary key in a database table is a field in the table that uniquely identifies every row or record present in the database table.

Example:

• Students in Universities are assigned a unique registration number.
• Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.

Foreign Key:

Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.

Example:

• In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.