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I felt this is the best place to ask this, rather than Stackoverflow as it is not related to programming.
Ok. The thing is I need to draw an ERD of a leave management system. Suppose there are three level of user roles there - Level A, B and C.
Where A can manage both B and C; B can manage only C and C is normal users.. Now I've specified an entity named USER in the ERD and thus have to maintain only one table in my database for all type of users and set a role flag and code according to that. But how exactly do I represent this three levels of users in an ERD, as the ERD has only one entity for USER? and role is just an attribute there?
Do I have to make three entities for three types of users and hence create three tables and continue like that? But I can manage all the functionalities with just one table and one flag.
Am a bit confused. Please do guide me. :)

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up vote 2 down vote accepted

You said it yourself, and gave it a good thought. Entity Relation Diagram. You have only one Entity of USER, thus you only need to put it once. Role is an attribute of that Entity.

I would digg deeper in the levels of roles in a Functional Diagram, where the Entities are used in a certain Functionality.

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