What I'm trying to do is map a tree structure.
I got groups that can have child groups, and the children can have their children and so on.

Here is how the database looks:

Groups

int Id
string Name

And then there is a pretty big problem. Here is the relations.

Group_Links

int ParentId
int ChildId

I have absolutely no clue about how to solve this and I can't change the existing database. There is already a lot of information in it. Have already tried a lot of things but can't get anything to work. Any help would be really appreciated! Thanks in advance!



Cheers,
Yagami

You can map it as a plain bag with a many-to-many association

<bag name="Children" ....>
<many-to-many class="Group" column=".." table="group_links"
</bag>

if you need a reference from the child group to the parent, you need another bag with a many-to-many association to the parent. You can use a private field for that and define a property that returns the single parent that will be in that bag.

The main problem is how to efficiently retrieve a larger part of the tree, because you can't use FetchMode.Join in that special case.

Thanks a lot for your reply! We have decided to wait with this and I'll continue with some other things that needs to be done.
The reason why this mapping problem exists is the database design is not quite what it should be in this case so it may be
possible to change the database if everything goes well.
I'll check out how well it goes with a many-to-many when done with the other things.


Thanks a lot for your help!