CODEWITHSUNDEEP
sqlentity-relationshiper-diagram
user6031489
user6031489

Reputation:

ER Diagram Entity without attribute

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:

enter image description here

Thanks

Upvotes: 3

Views: 8148

Answers (2)

reaanb
reaanb

Reputation: 10065

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.

Upvotes: 1

alexander.polomodov
alexander.polomodov

Reputation: 5534

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.

Upvotes: 2

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