Database relationships

Jeremy Vigil

August 18, 2002

Dbm/380

Instructor

Vicki Martin

Introduction

            There are three types of database relationships.  They are as follows.  (One to one, one to many, and many to many)  I will be explaining the differences between the different database relationships.  I will follow each relationship with and example.

One to One

            One to one is a direct relationship from one single item to another single item.  For example, when you hire an employee you will need an employee identification number for each employee.  One employee must have one employee identification number.  This will uniquely identify the employee for paperwork.  This can be the social security number or an identification number generated by the employer.

One to Many

            One to many is like a single tree with many branches.  One item is used to link many other different items.  The example I use here is one manager to many employees.  It only takes one manager to manage multiple employees. 

Many to Many

            Many to many is several items relating to several other items. This can include a restaurant menu to inventory.  A restaurant menu has many items that need to be related to the individual items.  The menu items can include hamburgers and salads while the individual items can include meat, lettuce, and cheese.  This is the many to many relationship.