NHibernate querying without mapping inverse relationships

In my neverending quest to keep my domain minimal, I ran into a query that I wanted to perform with NHibernate that seems to be impossible without adding an additional property and hbm mapping definition.

Note: I still consider myself rather new to NHibernate, so this might have an obvious answer.

Let's say I have following two classes:
public class School : EntityBase
{
     public string Name { get; set; }
     public IList<Student> Students { get; set; }
}

public class Student : EntityBase
{
     public string Name { get; set; }
}

The School.hbm.xml file contains this in the body:
<bag name="Students">
    <key column="SchoolId"/>
    <one-to-many class="Student"/>
</bag>

The database representation of the above looks something like this:
Db representation

Without making any changes to my classes/mappings, I can perform this SQL query to retrieve all Students who's name contains 'Powers' that belong to a school who's name contains 'Middle':
SELECT * FROM Students
WHERE
     Students.Name LIKE '%Powers%'
     AND
     Students.SchoolId IN (SELECT School.Id FROM Schools WHERE Schools.Name LIKE '%Middle%')

So - Here is the question, how can I do this in an HQL query without making any changes to my domain (which would be specifically adding a School property to the Student class and defining the relationship in the Student.hbm.xml file)?

2 Comments

  • You probably want to use the inverse anyway. Right now inserting a new student is two operations, instead of one, because NH has to update two reference.

    And it doesn't really make sense from a domain model point of view.

    That said, this HQL would solve the issue:

    select s from Student s
    where s.Name like '%Powers%'
    and s in (select i from School sc join sc.Students i)

  • Nhibernate querying without inverse relationships.. Peachy :)

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