An Entity Relationship Diagram, or ERD, is a visual representation of the relationships that tables have in a database. They are vital for the integrity of the database in that they define what attributes within and entity are directly related. In an ERD, the entities and its attributes are linked in order to establish the relationship that the entity has with the other entities in the database. Relationships such as one-to-one, many-to-one, and many-to-many are used to illustrate the relationship logic of a database (Kroenke & Auer, 2010). In Microsoft Access, the Relationships tool facilitates the creation of ERDs. Using the Relationships tool, users are able to define the relationships that each entity has with other entities in the database. For example, in the ERD shown below, lines that show their respective relationships with the other entities in the database connect the entities. A driver can be assigned to many addresses but only one address can be assigned to a driver at any given time. The relationship is the same with Emergency Contacts; a single contact can be assigned to many drivers but a driver can only be assigned one contact.
The ERD also demonstrates the relationships that other entities have with each other. One-to-one relationships exist in the ERD as well. Each driver can only have one Drug Test Record assigned to him or her. Each Drug Test Record belongs to the sole driver therefore only one can be assigned to any given driver. Deeper in the ERD, relationships are used to more efficiently store data in tables. Due to the overwhelming amount of attributes in the Huffman Trucking Entities and Attributes for Daily Driving Log, there are instances when a table must be split up into two or more tables to more efficiently organize the data. This process is known as Normalization. In the Driving Log entity, the attributes for Tractor Details, Co-Driver Details, and Trip Details were split up into three separate entities in...