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Entity- Relationship (E-R) Diagram


The overall logical structure of a database can be expressed graphically by an E-R diagram.

The diagram consists of the following major components.

  • Rectangles: represent entity set.
  • Ellipses: represent attributes.
  • Diamonds: represents relationship sets.
  • Lines: links attribute set to entity set and entity set to relationship set.
  • Double ellipses: represent multi-valued attributes.
  • Dashed ellipses: denote derived attributes.
  • Double lines: represent total participation of an entity in a relationship set.
  • Double rectangles: represent weak entity sets.

Summary of Symbols Used in E-R Notation


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