How to find the top father item in a BOM

[cr7dav]

Hi all,

I have a table where is stored only father item and child item. Something like this:

Father Child
itemB itemC
itemA itemB
item2 item3
item1 item2

I only need to create a two columns table with item and the relative top parent, like this:

item parent
itemB itemA
itemC itemA
item2 item1
item3 item1

could someone help me to achieve this target?

Thanks in advance