Entity Relationship

By Tiationg Kho |
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Entity Relationship

  • One-to-One
    • Relationship where a record in one table is linked to exactly one record in another table
    • eg. each student has a unique locker
  • One-to-Many
    • Relationship where a single record in one table can be associated with one or more records in another table
    • eg. each student belongs to exactly one department, but a department can have many students
  • Many-to-Many
    • Relationship where many records in one table are associated with many records in another table
    • Typically implemented using a conjunction table that contains foreign keys linking to the primary keys of the two tables involved
    • The conjunction table’s primary key is a composite key
    • eg. students can join multiple clubs and each club can have multiple students