Access数据库-为什么这是一对一关系？

Question

My understanding was that: a one-to-one relationship is created when both fields involved are primary keys.

In the case encountered below, I (believe I) have a relationship between a Primary Key and a Foreign key and this should be a one-to-many relationship. But Access is showing it as a one-to-one relationship, and will not allow duplicate entries on the many side.

What is the error in my understanding of this?

Answer 1

My understanding was that: a one-to-one relationship is created when both fields involved are primary keys.

Then I would suggest your understanding is wrong :-)

The target column doesn't have to be a primary key, it's sufficient that it be marked as unique. This would enforce one-to-one at the database level.