Relational Database Concepts
There all different types of relationships in our daily life which can be related to objects or humans. These relationships easily amalgamate in databases as well. Examples of relational concepts from our everyday life are discussed below.
A simple yet strong one to one relationship is ‘Tooth brushing’. In this the entities are a person and a toothbrush. This relationship is one to one because one person uses one toothbrush and alternatively, one toothbrush is used by one person only. This is a sort of example that everyone experiences daily. Each entity has only one relation to the other entity. (Chapple)
An example of one-to-many relationship would be the Law Enforcement. In this case the entities are the law (one) and the citizens (many). In this relationship, a single set of rules provides guidance and service to many citizens. The people are independent of each other but they are still governed under a unified law. This makes it possible to work and coexist in harmony because of a shared central relationship.
An example from newspapers of a many-to-many relationship would be the advertisers of the newspaper and the readers of the newspaper. Here the entities are the readers, the newspaper, and the advertisers. The linking entity is the newspaper in this case (TechRepublic, 2004). The newspaper has many different advertisers that publish their advertisement knowing that it would be read by many different people. Inversely, many readers will read the newspaper knowing that they will get to read a lot of advertisements. In this way many different entities are linked indirectly.
Chapple, M. (n.d.). Creating Relationships. Retrieved May 28, 2010, from About.com: http://databases.about.com/cs/tutorials/a/accessgup7.htm
TechRepublic. (2004, January 30). Define relationships between database tables. Retrieved May 28, 2010, from TechRepublic: http://articles.techrepublic.com.com/5100-10878_11-5141049.html