I am taking an introduction to database objects course at college.
I am in disagreement with the professor over how to interpret the Crow's Foot Notation for Cardinality in an ERD diagram.
Example: Look at this image (one I pulled from lecture slides):
According to my interpretation, this indicates that:
- A Supplier may have 0 or many Shipments
- A Shipment may belong to only one Supplier
- A Customer may have 0 or many Orders
- An Order may belong to only one Customer
However, according to my instructor's interpretation, this shows that:
- A Shipment may have 0 or many Suppliers
- A Supplier can have only one Shipment
- A Customer may have only one Order
- An Order may have many customers
I have been unable to find any evidence to contract my own understanding of this... but, again, I'm just a student. Maybe I'm missing something? If I am, I'd like to figure out where I went wrong.