ChildId Name ParnetId
1        a      -1
2        b      -1
3        c       1
4        d       3
5        e       2

ChildId ChildName ParnetID ParnetName GrandId GrandName
4        d          3        c          1       a
5        e          2        b

create table tableA
(childID int
,name char(1)
,parentID int
)

insert into tableA
select 1,'a',-1 union all
select 2,'b',-1 union all
select 3,'c',1 union all
select 4,'d',3 union all
select 5,'e',2


select 
G1.childID as G1_childID
,G1.name as G1_childName
,G1.parentID as G2_parentID
,g2.name as G2_parentName
,G2.parentID as G3_grandParentID
,G3.name as G3_grandParendName
into tableB
From tableA as G1 --generation1
 join tableA as G2 --generation2
on g1.parentID = g2.childID
 join tableA as G3 --generation3
on g2.parentID = g3.childID
where
g1.parentID > 0

union all

select 
G1.childID as G1_childID
,G1.name as G1_childName
,G1.parentID as G2_parentID
,g2.name as G2_parentName
,'' G3_grandParentID
,'' as G3_grandParendName

From tableA as G1 --generation1
 join tableA as G2 --generation2
on g1.parentID = g2.childID
where
g1.parentID > 0

union all

select 
G1.childID as G1_childID
,G1.name as G1_childName
,'' as G2_parentID
,'' as G2_parentName
,'' G3_grandParentID
,'' as G3_grandParendName

From tableA as G1 --generation1
where
g1.parentID > 0
--(7 row(s) affected)



select
x.*
into tableC
from (
select * from tableB
except
select * from tableB
where G3_grandParentID = G2_ParentID
or G2_ParentID = G1_ChildID
)x 
where x.g3_grandparentID > 0


select * from tableC
union all

select * from
(
select * from tableB
except
select * from tableB
where G3_grandParentID = G2_ParentID
or G2_ParentID = G1_ChildID
) as x
where
x.G1_childID > (Select G1_childID from tablec)