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Which is the redundant relationship in this ER Diagram and why? A few of my friends and I have been trying to figure it out but keep going in circles.

enter image description here

where the attributes of each entity are as follows:

Employee: Employee_No, Name, Address and Telephone_No.
Department: Department_No, Name and Location.
Training Course: Course Code, Title, Start_Date and Description.
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migrated from Jun 12 '13 at 13:38

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None of them are redundant, assuming they represent your requirements correctly. Can you tell us the requirements you are trying to model with this ER diagram? – Branko Dimitrijevic Jun 12 '13 at 11:11
The answer changes based on your assumptions which is why you have to explain your reasoning. – JamesRyan Jun 12 '13 at 13:55
As Branko said, we need the requirements (the conceptual model) to be able to determine if this logical model is correct or not. – Greenstone Walker Jun 12 '13 at 22:09

None of them are redundant. It's ok to have a loop.

You seem to be missing a many-many relationship (Employee Course) table, though.

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Assuming that employees only attend training courses for their department, you could derive the department an employee works in according to the training courses they've taken.

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And if an employee has not attended any training courses, we assume he hasn't been assigned to a department? Too many assumptions I think, that don't make much sense. – ypercubeᵀᴹ Jun 12 '13 at 20:03

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