CODEWITHSUNDEEP
databaseentityerd
user22712627
user22712627

Reputation:

Can a weak entity have more than one relationship with its supporting entity?

In ERD, can a weak entity have more than one relationship with its supporting entity?

If a weak entity can have more than one relationship with its supporting entity, can all of them be identifying relationships, or only one of them can be the identifying relationship?

Upvotes: 0

Views: 155

Answers (1)

Christophe
Christophe

Reputation: 73510

The weak entity can not be uniquely identified without reference to another entity. This means that a foreign key to another entity is part of its primary key.

As a consequence, a weak entity cannot have more than one identifying relationship with another entity. If it would, it's identity would no longer be unique.

However nothing prevents it from having ANOTHER, different , relationship to the same supporting entity. Let's take an example: a PROJECT is a strong entity. a TASK is a weak entity whose identity depends on the PROJECT. But a task could have a secondary relationship to PROJECT, not related to the task's identity, for example to express that a that a task is one project is to refer to a project.

Upvotes: 0

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