Need help setting up and iterating thru a tree


Newbie here. Given the following table named Employee_Links:

ID Emp_ID Parent_ID

1 200 100
2 300 100
3 300 200
4 400 100
5 500 400
6 500 300

I’d like to be able to generate a tree that looks like this:


Note that where 500’s Parent_ID = 300 (row 6), 500 is linked to the
first 300 it finds in the tree diagram.

After some experimentation, it appears that ACTS_AS_TREE won’t work
since I have nodes that will have >1 parent node. Is there a simple way
to setup the relationship (HABTM?) AND the code that generates the tree
diagram? I’ve looked at various similar examples online, and I have the
new Rails Recipes PDF book, but I haven’t been able to figure this one
out without writing a lot of code, which I have a feeling is the wrong