First, you should understand one thing. Many-to-One and One-to-Many are different relationship types.

Many-to-One

It’s a simple foreign key. In a many-to-one relationship, many records in one table can be associated with a single record in another table. It's the main relationship type in relational databases.

In the example, each Student has a reference to the School (it is represented as school_id).

One-to-Many

It’s a relationship where one table references many other tables. This one table has a list of primary keys as the one foreign key. This relationship is rare for relational databases and cannot set strong dependencies. So, it’s a bad practice, but it can be used in non-relational databases.