(Fluent) NHibernate: Map field from separate table into object - nhibernate

Question

I'm currently trying to get (Fluent)NHibernate to map an object to our legacy database schema. There are three tables involved.
Table a contains most information of the actual object I need to retrieve
Table b is a table which connects table a with table c
Table c has one additional field I need for the object
An SQL query to retrieve the information looks like this:
SELECT z.ID, z.ZANR, e.TDTEXT
FROM PUB.table_a z
JOIN PUB.table_b t ON (t.TDKEY = 602)
JOIN PUB.table_c e ON (e.ID = t.ID AND e.TDNR = z.ZANR)
WHERE z.ZANR = 1;
The main problem is how to specify these two join conditions in the mapping.
Entity for table a looks like this:
public class EntityA
{
public virtual long Id { get; set; }
public virtual int Number { get; set; }
public virtual string Name { get; set; }
}
Name should map to the column table_c.TDTEXT.
The mapping I have so far is this:
public class EntityAMap : ClassMap<EntityA>
{
public EntityAMap()
{
Table("PUB.table_a");
Id(x => x.Id).Column("ID");
Map(x => x.Number).Column("ZANR");
}
}
I tried to map the first join with the same strategy as in How to join table in fluent nhibernate, however this will not work, because I do not have a direct reference from table_a to table_b, the only thing connecting them is the constant number 602 (see SQL-query above).
I didn't find a way to specify that constant in the mapping somehow.

Answer 1

you could map the name as readonly property easily
public EntityAMap()
{
Table("PUB.table_a");
Id(x => x.Id).Column("ID");
// if ZANR always has to be 1
Where("ZANR = 1");
Map(x => x.Number).Column("ZANR");
Map(x => x.Name).Formula("(SELECT c.TDTEXT FROM PUB.table_b b JOIN PUB.table_c c ON (c.ID = b.ID AND b.TDKEY = 602 AND c.TDNR = ZANR))");
}
Update: i could only imagine a hidden reference and the name property delegating to there
public EntityAMap()
{
HasOne(Reveal.Member<EntityA>("hiddenEntityC"));
}
public class EntityB
{
public virtual int Id { get; set; }
public virtual EntityA EntityA { get; set; }
}
public EntityCMap()
{
Where("Id = (SELECT b.Id FROM PUB.table_b b WHERE b.TDKEY = 602)");
References(x => x.EntityA).PropertyRef(x => x.Number);
}