derived query

Hi,
I have a table CH in SQL Server 2005 with columns ParentID (PK) and childID. ChildID could be the ParentID of Another ChildID. I want all the ChildID that are also the ParentIDs.

I have tried this:
Select ParentID From  (Select ChildID from ch) ch
   
But it does not work.
SA4Asked:
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gpompeCommented:
Try this
select a1.ChildID from Ch a1 join Ch a2 on a1.ChildId=a2.ParentID
0

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Guy Hengel [angelIII / a3]Billing EngineerCommented:
please try this:

WITH R ( ParentID, ChildID, Level )
AS (
   SELECT ParentID, ChildID, 0
   FROM CH
   WHERE ParentID IS NULl
UNION ALL
   SELECT c.ParentID, c.ChildID, R.Level + 1
   FROM R
   JOIN CH
     ON R.ChildID = CH.ParentID
   )
SELECT *
FROM R

http://www.eggheadcafe.com/articles/sql_server_recursion_with_clause.asp
0
SA4Author Commented:
thanks for the reply, I tried this:
WITH R ( ParentID, ChildID, Level )
AS (
   SELECT ParentID, ChildID, 0
   FROM CH
   WHERE ParentID IS NULl
UNION ALL
   SELECT c.ParentID, c.ChildID, R.Level + 1
   FROM R
   JOIN CH
     ON R.ChildID = CH.ParentID
   )
SELECT *
FROM R

But It does not give any result And I know that there are a few that I should be getting.
 
0
jrb1senior developerCommented:
select parentid from ch where parentid in (select cihldid from ch)
0
SA4Author Commented:
thanks for your help.
0
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Microsoft SQL Server 2005

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