I've been trying to solve a mapping problem for a few weeks with no luck. I know this is something simple, but I'm just not using the right terminology.

I have a Teacher class and a Student class (with corresponding database tables Teachers and Students). I have a TeacherStudents table that simply maps TeacherID to StudentID in a one-to-many fashion (one Teacher for many Students). I'd like to add an Advisor property to the Student class that uses the TeacherStudents table to get the Teacher mapped to the Student.

How would I go about this?

It looks like your Teacher and Student are linked by a many-to-many relationship...

As a student can have many teachers, how do you choose the Advisor?

The classic solution to this problem is to add an Advisor column in your Students table (FK of Teachers) and map it as a many-to-one.

A Teacher can have many students, but a Student should be mapped to just one teacher. Adding an Advisor column to the Students table is a solution, but it seems like a duplication of the mapping that already exists in the TeacherStudents table.

What I'm looking for is something that would show up in the Students.hbm.xml file and look like this:

<relationship name="Advisor" table="TeacherStudents" my_column="StudentID" other_column = "TeacherID" class = "Teacher" />

I don't understand why you need the TeacherStudents table.



This is a <one-to-many> relationship:
- Add a 'Teacher' column in your Student table
- Add a MyTeacher/MyAdvisor property in the Student class (of the type Teacher) + Map it as a <many-to-one>
- Add an IList in your Teacher class and map it as a <bag inverse="true">
...

Thank you very much for the response. Using the bag solves a lot of similar issues I was having as well. I didn't quite understand its use before.