Re: Drawing arcs on ER diagrams

Liz J wrote:
> Hi
>
> I am learning about arcs on a ER diagram. Please could someone explain the
> significance of the circles that are on some of the arcs but not others?
>
> thanks
>
> Liz
>
>

There are no standards when it comes to ER diagrams. As such, the textbook or software you are using should explain this in more detail.

I some ER diagrams I have seen, the circles denote a connector from one page to another. The number in the circle would represent the page number where the ER diagram is continued. In other ER diagrams, the circles have denoted the "cardinality" of the relation, that is if the relation is 1-to-1, 1-to-many, or many-to-many. Finally, I have seen circles to denote the attribute names of an entity.

HTH,
Brian

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Brian Peasland
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