2 relationships between 2 entities in ER diagram

database database-design entity-relationship database-schema
user1330217 picture user1330217 · Jan 27, 2013 · Viewed 37.8k times · Source

I'm trying to draw an ER diagram describing the following:

-"Department" employs "Employees"

-Some "Employees" are "Special" and have more attributes

-Some of the "Employees" ("Special" and non special) are "Managers"

-"Managers" manage "Departments"

So, to convey this I have:

Department ------(employs)------- Employee-----<--------Special
      |                             |
      |-----------(manages)----------

From my understanding, I cannot have 2 relationships between 2 entities. How do I deal with this situation then?

Answer

High Performance Mark picture High Performance Mark · Jan 27, 2013

There is no reason you can't have multiple relationships between the same two entities, your understanding is wrong in this respect.

You have to be certain, of course, that the relationships capture different information and that you haven't, say, mistaken the two aspects of a single relationship as two different relationships. Your example seems to be a good candidate for having two relationships between the two entities.

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