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Relationship Strength

19 十月, 2015 - 16:06

Relationship strength is based on how the primary key of a related entity is defined.

Weak Relationships (non-identifying relationship)

  • Exists if the PK of the related entity does not contain a PK component of the parent entity.
  • Customer(custid, custname)
  • Order(orderID, custid, date)

Strong Relationship (identifying)

  • Exists when the PK of the related entity contains the PK component of the parent entity.
  • Course(CrsCode, DeptCode, Description)
  • Class(CrsCode, Section, ClassTime…)