Database Design Diagram

Hi y'all, I was just wondering, before implementing the real database, would you suggest that we make a diagram for it first?

If yes, then please state the type of diagram beside ERD and Class diagram.

I'm a little confused in trying to create one because we've already made an ERD and Class diagram which already give an outline of the database tables and attributes. But we still need to do another Database Design Diagram.

P.S Yes, I'm a CS student.

Well - it is tricky indeed.
I'll say it depends on the task at hand and the focus of the project, and the development methods used for the project. Scope is also a part to consider.
Especially because it is a educational project, there is also the time-constraint whether it is worth to actually include such a diagram compared to simply argue the points.
So it will be pretty much impossible to give a straight answer :)

If optimizing performance in the database is a part, then I'd most certainly include a database diagram, so you can map out which querys will be performed and thus which indexes to build while mapping out the database.

If not, then I'd personally - in an educational situation - use a class diagram as foundation for the database. I never made a project without a class diagram, well - once but then we were following a design method which didn't include class diagrams in its method. (was not an OO method).

So if database performance/design is not a (significant) part of the project you are working on, I'd properly then argue that the database diagram would be very similar to a class diagram and instead mention when I would make it and why. But because of the focus of the project, combined with the time-constraints I would not make it.

But as said - the "right" answer, the text-book answer if you will, is yes - it should be included.
But the pragmatic answer (and more often then not real life answer) is - depends on the scope and properly not. As long as you argue the why and why nots. :D