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What is the difference between ERD 1 and ERD 2?

From what I understand is that ERD 2 has the many to many relationships resolved with a link entity whereas ERD 1 only shows the relationship... is there anything else?

And also at which stage do you conduct normalization.


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closed as unclear what you're asking by Jack Douglas Nov 20 '13 at 17:52

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.If this question can be reworded to fit the rules in the help center, please edit the question.

Can you add some more detail, or a link to what you're talking about? As written, this question doesn't make a whole lot of sense. –  Simon Righarts Mar 4 '12 at 23:45
I don't use ERD myself (because they only show one flavour of constraint i.e. foreign keys) but I would have thought that normalization must be completed before you can product an ERD. –  onedaywhen Mar 5 '12 at 10:56
@onedaywhen Only showing one flavour of constraint is arguably an advantage of ERDs. When you are trying to understand how your entities are interrelated you don't want a lot of "noise" from other information. Of course ERD is not suitable as (nor is it intended to be) a comprehensive source of schema documentation. It isn't good at everything, but it is great at what it's for! Nevertheless, +1 for normalization before drawing the ERD. –  Joel Brown Mar 5 '12 at 15:15
I can't find any reference to ERD "1" or "2" with a quick Google - where have you come across the terms? –  Jack Douglas Apr 7 '12 at 11:18

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