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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.


The first one is traditional Chen's notation. The second one is modern Crow Foot or Baker's notation, used today by majority of tools and people. It is perferred because it is more readable and uses less space.


One can say that a proper entity-relationship diagram is that which was created using the constructs introduced by Dr. P. P. Chen (e.g., rectangular and diamond-shaped boxes) in his famous 1976 paper entitled The Entity-Relationship Model—Toward a Unified View of Data. Regarding your specific comparison, the illustration displayed in Figure 1 looks much ...


I am still learning myself so you might not agree with everything I say. In my business we have 'projects' that last for a certain amount of time and have staff assigned to them. I would give your Employees a 'default role' eg Manager, Technician whatever. Then when they are added onto a project this role will be used by default in a drop-down menu unless ...

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