Data Cardinality

Question

I'm confusing about 0:M relationship.

So, I want to ask about that.

Assumes we have 2 tables :

Contact which has attributes like : ContactID(PK), Name

Address which has attributes like : AddressID(PK), Desc, ContactID(FK to Contact, Nullable, Not Unique)

Is my statement right that :

• The 0:M relationship occurred when there is 1 row in Contact and it's ContactID don't appear in Address.

• To make the 0:M relationship Column ContactID in Table Address must be nullable.

Thanks in advance