Example and illustration about redundant relationships (MER)

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Context

Consider the sentence below:

It is claimed:

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

Doubt

Could you imagine a mental drawing of that sentence? I tried and gave it:

inserir a descrição da imagem aqui

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

How did it come about?

The question arose after answering this question of proof

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

database modeling relational-model relationship

  • May I suggest a more meaningful title? There’s some information in that question more relevant than just the fact that it’s a contest. For example, you could ask what are "redundant relationships" and by source of doubt this question, then enter the secondary objectives of the question that would remove the other options as valid

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    I think it is not enough to know only the concept about redundant relationships to answer the question, and I put the direct answer to make it easier for someone to try to justify the feedback. I didn’t know which title to put, so it got a little generic, think better to change to " What are redundant relationships ?"

  • I believe that this title can be useful yes. If through it you can bias in order to answer all your questions, it is valid. But don’t just take my voice as the ultimate factor, I’m trying to make it more attractive, but your need first. And secondly, not all people have my aesthetic sense, so maybe my suggestions can make it more attractive to other people’s eyes

  • @Jonathasb.C., does not have a graphical representation for this. The definition given in the question of the contest is somewhat complex and even confusing. I had to read it several times to understand it. I left an answer with two examples for you.

1 answer

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Redundant relationships are those unnecessary ones that don’t need to exist for you to be able to come up with information. Analyzing the definition with a different reading, we have that if we arrive at a result through the relationship between several entities, we would not need a new relationship to represent it (because the other relationships already define it).

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

Example 2: MER para Controle de Álbuns de Música

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 browsing other relationships ALBUM->TRACK->MUSIC->AUTHOR.

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    Excellent answer, thank you.

  • You’re welcome @Jonathasb. C.

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