Finding Top level parent of each row of a table [SQL Server 2008]

Question

I have following two tables

Table Person

Id   Name
   1    A
   2    B
   3    C
   4    D
   5    E

Table RelationHierarchy

Answer 1

Another way to do this in a loop if you wanted to work with sets is:

SELECT *
    INTO #parentchild
from RelationHierarchy 


WHILE EXISTS
(select 1 from  #parentchild A inner join #parentchild B on A.ChildID = B.ParentID Where A.ParentID <> B.ParentID )
BEGIN
update B set B.ParentID = A.ParentID
from #parentchild A inner join #parentchild B on A.ChildID = B.ParentID
END

select * from #parentchild