Is it possible to distinguish between identifying and non-identifying relationships using the Crow's Foot notation?

Case in point: In table Book, part of the book's Primary Key is a FK to the Author table. In other words I embed the author's identifier in the book's identifier. Also, a book has a FK to a Book_Type (containing values like "hardcover", "papercover") (this is just an example, I understand that I would probably need a "book edition" table for that).

The thing is that this latter FK relationship isn't nearly really as important as the former one (the FK to Book_Type is not part of Book's Primary Key), yet my understanding is that in the Crow's Foot diagram shown below, both these relationships are rendered identically:

enter image description here

Have I misunderstood something or is there a way to signify the identifying versus non-identifying relationship distinction using the Crow's Foot notation?

  • An Entity-Relationship Diagram (ERD), of which "crows-feet" is just one type of notation, describes only the relationship between entities. The Primary Key (PK) of an entity can normally be inferred from that but there are things you can do in creating a PK that are not clearly reflected in an ERD. By making the Book PK consist of the Author PK plus something else that is not a foreign-key (FK) (you didn't what) you are describing one of those. It would be much more flexible to just use auto-generated sequence numbers for the FKs of all tables. May 28, 2014 at 8:22

3 Answers 3


Information Engineering methodology placed a big "I" on the relationship to show the foreign key was part of the primary key:

enter image description here


Different ERD notations offer different relationship decorations for identifying relationships. The most common that I've seen is the use of solid lines for identifying and dashed lines for non-identifying.


In your diagram, you are showing both entities as solid lines indicating identifying relationships. Non-identifying relationships are shown with dashed lines.

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