How to use components in fluent nhibernate

I'm working on a legacy MySql database and have the following entities:

public class Company
{
     public int Id { get; set;}
     public string Address { get; set; }
     public string City { get; set; }
}

public class CompanyDepartment
{
     public int Id { get; set;}
     public string Address { get; set; }
     public string 开发者_StackOverflow社区City { get; set; }
}

The idea is that a company only use the department class if it has more than one department.

Right now I'm trying to make a company/department search, this means I need a list of all departments and therefore I need to "create" departments of all the companies that only has one department, and therefore don't have a entry in CompaynyDepartment.

To do this I was thinking of use components in fluent NHibernate, but I'm not sure I can join the real departments with the fake ones?

Is there a better approach to this problem? It's not an option to change the database structure.

I ended up changing the database structure