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Weak Entity Types

Weak Entity Types. CSCI 6442. Most entity types are strong entity types, that exist independently from other entity types A strong entity type always has a unique identifier that distinguishes each occurrence of that entity type A weak entity type needs another entity type for its identifier

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Weak Entity Types

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  1. Weak Entity Types CSCI 6442

  2. Most entity types are strong entity types, that exist independently from other entity types • A strong entity type always has a unique identifier that distinguishes each occurrence of that entity type • A weak entity type needs another entity type for its identifier • The entity type on which the weak entity type depends is called the identifying owner

  3. Example Dependent Employeeee belongs

  4. The identifying relationship is the relationship between a weak entity type and its owner • The weak entity identifier is its partial identifier combined with that of its owner.

  5. Types of Weak Entities • Existence-dependent entities—existence depends on existence of another (strong) entity • Associative entities—a many-many relationship • Subtype entities—entity type that inherits its identity from a supertype

  6. Example Course Student registers Party Employee Company

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