Entity relationship diagram

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Key points

  • Entity-relationship diagrams can be used to show the relationship between different tables in a relational database.
  • The links between tables show how one entity relates to another. The number of entities that relate to another is called its cardinality.
  • A one-to-one relationship is written as 1:1
  • A one-to-many relationship is written as 1:M
  • A many-to-one relationship is written as M:1
  • A many-to-many relationship is written as M:N



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