Weak Entities

What two conditions essential be met before an entity can be classified as a indistinct entity? Give an habit of a calorie-free 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 live on without the entity with which it has a alliance. 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 another entity as it cannot be uniquely identified by its own attributes alone. This means an gravel of one entity cannot exist unless thither is an occurrence of a middleman entity. This modeling situation commonly 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 electrical shaver entity.

Assume my companys HR decides it would be great to come out my kids a postcard for their birthday, so they will keep entropy nigh kids on their DB. They could guide for their SSN, but many employees would not ask to provide that information, so they may opt for let the dependent be a weak entity. This means the dependents would not unavoidably be discrete from each other only if by their information on the DB, but all dependents from the kindred employee enquire to be distinguishable. References Entity kin Modeling, www.siue.edu Advanced ER Modeling, www.spsu.edu Database Systems, Coronel/Morris/RobIf you wishing to take hold of a full essay, order it on our website: Orderessay

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