Sunday, October 10, 2010

Entity-Relationship Diagram 4.4


The diagram displayed above is an Entity-Relationship diagram.  An entity-relationship diagram is used to display the structure of data and show relationships between the entities.  Entities are what the data itself represents.  For example, Customer, Product, and Invoice are all entities because they are all nouns.   Below each of those entities are attributes or individual pieces of information about that entity in a database.  Data types are numbers or text that describe each of those individual attributes.  All of those attributes within each entity make up a record or a collection of related attributes.  The relationships are shown between each entity by an arrow or a line describing that relationship between each entity.  It could also be from attribute to attribute.

With all of this, we can make a database table in Microsoft Excel to emphasize the diagram greatly.

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