Meaning of "n:m" and "1:n" in database design

What does the letter 'N' on a relationship line in an Entity Relationship diagram mean? Any number

M:N

M - ordinality - describes the minimum (ordinal vs mandatory)

N - cardinality - describes the miximum

1:N (n=0,1,2,3...) one to zero or more

M:N (m and n=0,1,2,3...) zero or more to zero or more (many to many)

1:1 one to one

Find more here: https://www.smartdraw.com/entity-relationship-diagram/

Imagine you have have a Book model and a Page model,

1:N means:
One book can have **many** pages. One page can only be in **one** book.


N:N means:
One book can have **many** pages. And one page can be in **many** books.