新建文本文档 (3).txt - The entity must be existence-dependent on its parent entity The entity must inherit at least part of its primary key from

新建文本文档 (3).txt - The entity must be...

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The entity must be existence-dependent on its parent entity. The entity must inherit at least part of its primary key from its parent entity. For example, CLASS is clearly existence-dependent on COURSE. A strong relationship exists when en entity is existence-dependent on another entity and inherits at least part of its primary key from that entity. The Visio Professional software shows the strong relationship as a solid line. In other words, a strong relationship exists when a weak entity is related to its parent entity A composite entity is generally used to transform M:N relationships into 1:M relationships. A composite entity, also known as a bridge entity, is one that has a primary key composed of multiple attributes. The PK attributes are inherited from the entities that it relates to one another. A customer can own many cars. Some customers do not own cars. A car is owned by one and only one customer.
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  • One '11
  • JamesHarland

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