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I am not that much good at database diagraming. Whenever I am asked to create an ERR Diagram, I use MySQL WorkBench software.

However today I ended up in a conclusion when I see different types of ER Diagrams. My diagrams (designed via MySQL WorkBench) are like below.

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And I saw other types of ER Diagrams like below.

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Can someone please confirm which ER Diagram model should I use?

PeakGen
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  • @SergioTulentsev: Sorry, what I meant by 'correct' is "which model you should use", "when someone asked you to give an ER Diagram, which diagram model you should give", – PeakGen Sep 08 '14 at 08:45
  • @SergioTulentsev: I can see that lot of software including "Astah Professional" also draw the ER Diagrams like the first one, which is similar to MYSQL WorkBench. – PeakGen Sep 08 '14 at 08:51
  • Either one should serve. It's not the look that matters, but the data. – Sergio Tulentsev Sep 08 '14 at 08:51
  • @SergioTulentsev: You have answered to lot of DB questions and an DB Expert, so mind providing a bit more detailed answer because I know lot of people get confused with these. The diagram like the first one also considered as EER Diagrams, why is it? – PeakGen Sep 08 '14 at 08:58

2 Answers2

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An Entity Relationship Diagram is an example of a presentation of a Conceptual Model. A Conceptual Model is used to help people understand the subject area(s) the model represents. Therefore, the correct presentation of a Conceptual Model - which may be or include an Entity Relationship Diagram - is one that all interested parties are satisfied adequately explains these subject areas. These interested parties should include potential users of a system that incorporates the subject areas, managers of these areas and IT professionals who will be designing and building a system covering these areas.

The agreed Conceptual Model is then taken by the IT professionals and formalized into a Logical Model, which may be presented as a Relational Data Model.

DrabJay
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  • Thanks for the reply. In simple terms, what you say is `The model to be used is based on the interest of all the parties. Therefore, no one can say which model is the most suitable one` Am I correct? – PeakGen Sep 08 '14 at 09:59
  • Not quite. It is the interested parties who can say which diagram is most suitable i.e. if you have been asked to produce an ERD for a project it is the project stakeholders who should say if they are satisfied with the Conceptual Model you have produced. I cannot say which one of the above you should use, as I am not a stakeholder in your project. – DrabJay Sep 08 '14 at 10:13
  • I agree with this answer. However, it should be noticed that many professionals tend to use ER diagramming tools and techniques when preparing a picture of a relational model. I'm going to go so far as to say that the majority of ER diagrams presented in SO and in DBA.SE are really diagrams of a relational model and not of an ER model. It's easy to conflate the two. – Walter Mitty Sep 09 '14 at 10:26
  • I also want to point out that there are stakeholders who need to get the conceptual model, and even critique it with regard to veracity, but who do not need to understand the role that foreign keys and junction tables play in the relational model. The ER model is good for this purpose. – Walter Mitty Sep 09 '14 at 10:29
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Actually both of them are ER diagrams. However, the second one is its scientific representation. MySQL use a representation which is more understandable way of it.

boddza
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  • Thanks! Some people call the MYSQL Diagram is more about an EER Diagram, why is it? I also prefer MySQL Diagram, going to send it to the department bcs they asked me for the ER Diagram. – PeakGen Sep 08 '14 at 08:59