ER Diagram Entity without attribute

Question

I have designed an er-diagram and have an entity without any attributes. I need this entity (Item) to create a many-to-many relationshop but I guess there is a way to make this more efficient and getting rid of the entity without attributes.

ER DIAGRAM:

Thanks

Answer 1

As I can see from your diagram your Item isn't just entity without attributes. It's a base type for your BAGEL and DRINK (you can think of this relationship as inheritance in OOP languages).

There are some techniques to work with inheritance in database world . So this Item is not a problem for ER-diagram .

Answer 2

ITEM should have at least one attribute - an identifier. A supertype's primary key can be reused as a foreign primary key in its subtypes.