Fluent NHibernate - mapping multiple levels of inheritance with multiple discriminators

Question

With the following class hierarchy - what would the DiscriminateSubClassesOnColumn("").Formula([insert custom sql here]) statements look like?

public abstract class Base
{
    public virtual string FEE_IND { get; set; }
    public virtual string REC_PAY { get; set; }
}

//  FEE_IND == "03"
public abstract class Child : Base
{}

//  FEE_IND == "03"
//  REC_PAY == "P"
public class ChildChild : Child
{}

I haven't been able to find anything that I could wrap my head around.

Answer 1

.Formula("Concat(FEE_IND, REC_PAY)")

// Child
.DiscriminatorValue("03");

// ChildChild 
.DiscriminatorValue("03P");