Example and illustration about redundant relationships (MER)

Question

Example and illustration about redundant relationships (MER)

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Context

Consider the sentence below:

It is stated:


Relationships that are a result of combining other relationships between the same entities are called: redundant relationships

Doubt

Would it be possible to imagine a mental drawing of this sentence? I tried and gave it:

Can anyone find a better way to represent? or an explain with some example?

How did it come about?

The doubt arose after answering this question of proof

Source: Evidence: FCC - 2012 - TRE-CE - Judicial Analyst - Systems Analysis Discipline: Database (IT) - Subjects: MER (Model Entity Relationship)

modelagem modelo-relacional relacionamento entidade-relacionamento

asked by anonymous 30.10.2017 / 22:36

1 answer

Write dates (month / year) between two dates PDO - Which is better: columnCount or rowCount? [closed]

score 0 · Accepted Answer

Redundant relationships are those unnecessary ones that do not need to exist for you to get to information. Analyzing the definition with a different reading, we have to reach a result through the relationship between several entities, we would not need a new relationship to represent it (since other relationships already define it).

Example 1: [TEACHER] ministers [COURSE] and [STUDENT] does [COURSE], the first with cardinality 1-N (assuming an exclusive teacher for 1 course) and the second with N-N cardinality. With this configuration, I know who is the teacher of any student, without having to make a redundant relationship between student and teacher for this.

Example 2:

In this case, for example, I would have a redundant relationship if I created a relationship between ALBUM and AUTHOR only to know which author is part of each album. I already get this by navigating the other relationships ALBUM- > TRACK- > MUSIC- > AUTHOR.