Database Design – The ER Model

The Entity-Relationship Model is a data model that helps us describe the organization of data for a particular scenario (business, or some other need).  It was developed by Peter Chen and originally published in 1976.  What we get is an abstract representation of the data by viewing the problem in terms of entities and relationships (that exist among the entities).  Here are some good references for the ER Model:

Some terms and concepts to pay attention to:

  • Entity vs. Entity Set
  • Relationship vs. Relationship Set
  • Attribute
  • Key, Primary Key, etc.
  • Relationship Cardinalities (1:1, 1:M, M:N)
  • Relationship Constraints (Total or Partial)

Different ER Model Notations:


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