Weak Entities

What two conditions must be met before an entity can be classified as a indistinct entity? Give an workout of a run-down entity and a detailed explanation of what a weak entity is and how a decision to use a weak entity might be made. 1. It can non exist without the entity with which it has a relationship. 2. The entity has a regular key that is partially or totally derived from the parent entity in the relationship. A weak entity is an entity that must defined by a foreign key relationship with a nonher entity as it cannot be uniquely identified by its own attributes alone. This means an stance of one entity cannot exist unless there is an occurrence of a subsume entity. This modeling situation usually occurs for binary 1: N relationships where the cardinality is mandatory-one for the weak entity. The weak entity is referred to as the unfree or electric shaver entity.

Assume my companys HR decides it would be great to get away my kids a postcard for their birthday, so they will keep info nigh kids on their DB. They could ask for their SSN, but many employees would not ask to provide that information, so they may opt for allow the dependent be a weak entity. This means the dependents would not unavoidably be distinguishable from each other but by their information on the DB, but all dependents from the equal employee enquire to be distinguishable. References Entity Relationship Modeling, www.siue.edu Advanced ER Modeling, www.spsu.edu Database Systems, Coronel/Morris/RobIf you regard to take hold of a full essay, order it on our website: BestEssayCheap.com

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