An ERD is an Entity-Relationship Diagram. This diagram is a tool that can be used to identify the relationship between certain entities. These entities include things such as people, things, or concepts within a database. This diagram can prove to be useful for businesses as it helps to demonstrate the existing database, provides a visual aid for bug fixes, and provides a road map to design from as a new database or even update the old one. Within this diagram there are a few common symbols, they are:
Entities: represented by rectangles, and is an object or concept
Relationships: represented by diamonds, shows how two things share information
Attributes:represented by ovals, a characteristic of an entity (i.e. social security number, etc.)
Connecting Lines: solid lines connecting attributes and entities
Cardinality: the number attributed to the relationship. (i.e. one-to-one, many-to-one, etc.)
Furthermore, there are three types of ERD models.
Conceptual ERD: includes the entity and relationship
Logical ERD: includes the entity, relationship, and attribute
Physical ERD: includes the entity, relationship, attribute, attribute types and key.
The determination on which model is used is based on the businesses needs. If a business is looking for a high level view of a project, a conceptual ERD will likely be used. If a business is looking for a ground level view with technical details, a physical ERD would be the most useful choice.
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Hey, Robert. I liked how you further expanded on the definition of an ERD and gave more detail than we covered in class. I personally did not know about Logical ERD and Physical ERD.
Hi Robert, I really appreciated how you broke down different aspects of ERD diagrams piece by piece here. With you separating different types of ERDs and the symbols they hold, it gave me a better understanding on how to utilize them and read them. I also liked how you broke down the 3 types of ERD models as sometimes I did get confused with the differences of the 3 and when they need to be used.