Week 2 DQ 2
University of Phoenix
DBM500: Database Concepts
August 24, 2007
How do Entity Relationship Diagrams (ERDs) help to ensure proper database design?
The importance of proper database design was addressed in DQ1 of this week. Entity Relationship Diagrams (ERDs) help ensure proper database design by graphically showing the structure of a database.
ERDs also help us learn key concepts about the data we need to use or manipulate. For example, ERDs indicate:
1. data relationships such as One-to-Many, Many-to-Many, Ambiguities
2. what data needs to be stored
3. the degree of a relationship
The ERDs helps us evaluate the design and to understand areas that may be of concern, or areas we may have missed.
In an online lecture, Data Modeling with Entity Relationship Diagrams by Frances Wickham from the Medical University of South Carolina (http://www.srnr.arizona.edu/rnr/rnr417/erdiagrams3/erdiagrams.htm)
Wickham indicates that data models such as ERDs are used as communication tools and also, "provide the developer an opportunity to work out conceptual and design issues and problems prior to beginning the actually design process."
Wickham compares building a database to constructing a building, the ERD is the blueprint from which the database will be built, and "no reputable builder would start to construct a building without a detailed blueprint."
An entity is a person, place or thing about which data can be stored for tracking by the user. For example, an entity can be a customer, and the data that will be stored for that entity can be: the customer's account number, the customer's name, the customer's address and the customer's phone number.
Relationship is the interaction between entities. For example, a customer which is an entity places an order at the company's web-store which is also another entity. Placing the order is the link between the two...