Hi,

I'm using NHibernate 1.2.1 and I've got a question concerning compositeId and a many-to-one relation:

Object A has got a composite id (Id1 and Id2). Some other object are implementing a many-to-one relation and are accessing to this object through the composite id. Everything's fine.

Object A (excerpt)


Any other Object accesses to it by:


But the evil Object B has also a many-to-one relation and want's to access to object A, but only by using the first part of the composite id (Id1), because the use of both keys would return a different set of data.



I've got an error when I try create my nhibernate session saying "Foreign key in table B must have same number of columns
as referenced primary key in table A". I understand what this means cause I normally use both parts of the composite id. But is there a way only to use one part of the key and ignore the second?

As I'm dependend to an existing data model and as I'm not mighty to change this data model, I'm searching for a way to connect my objects through this many-to-one relation using only the first part of the composite-id.

Any ideas, hints or remarks?
Thanks, aggn

NHibernate usually only allows foreign keys (many-to-one references) to primary keys. But if you know that some property other then the primary key is unique in the referenced entity, you can use the attribute "property-ref" on your many-to-one relation.

From the documentation:


But such a reference would only work if you have a unique constraint on the column TableA.ID1 in your database!

Thanks for your reply! I'll check that and give you some feedback.

Meanwhile I'm wondering, if this will also work with more than one column. E.g. I've got a composite id out of four parts but only want to refer to the first two keys...

... I've got a really ugly datamodel here...

You're welcome.


I couldn't find something about that in the documentation, so I'm afraid that won't work.


Agreed ;-)