Entity Relationship Diagramming

Posted by Ben Aston on Stack Overflow See other posts from Stack Overflow or by Ben Aston
Published on 2010-04-19T08:57:40Z Indexed on 2010/04/19 11:23 UTC
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data-modelling

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er-diagrams

I'd like to improve my understanding of cardinality constraints in ER diagrams.

I have two entities:

User
Location

But, I want the relationship between these two entities to be many-to-many (a user can be in many locations and a location can have many users).

To do this I need to introduce an association class UserLocation.

Is it correct to say I now have 3 entities?

If I were to draw an ER diagam of the above, would I draw in the UserLocation entity, and would the cardinality look like this?

User 1 ------ * User Location *  ------ 1 Location

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