CTE to traverse back up a hierarchy?

Question

I can find all the children of a given record in a hierarchical data model (see code below) but I'm not sure how to traverse back up the Parent/Child chain with a given Child ID. Can anyone point me in the right direction to figure out how to do this? Is this possible in Linq to SQL as well?

WITH TaskHierarchy (TaskID, [Subject], ParentID, HierarchyLevel, HierarchyPath) AS
(
   -- Base case
   SELECT
      TaskID,
      [Subject],
      ParentID,
      1 as HierarchyLevel,
      CONVERT(VARCHAR(MAX),'/') AS HierarchyPath
   FROM Task
   WHERE TaskID = 2

   UNION ALL

   -- Recursive step
   SELECT
      t.TaskID,
      t.Subject,
      t.ParentID,
      th.HierarchyLevel + 1 AS HierarchyLevel,
      CONVERT(varchar(MAX),th.HierarchyPath + CONVERT(VARCHAR(32),t.ParentID) + '/') AS HierarchyPath
   FROM Task t
      INNER JOIN TaskHierarchy th ON
         t.ParentID = th.TaskID
)

SELECT *
FROM TaskHierarchy
ORDER BY HierarchyLevel, [Subject]

Answer 1

Ah, I figured it out:

WITH Hierarchy(TaskID, [Subject], ParentID, IsProject, HLevel)
AS
(
    SELECT 
     TaskID, 
     [Subject], 
     ParentID ,
     IsProject,
     0 as HLevel
    FROM 
     Task 
    WHERE 
     TaskID = 59

    UNION ALL

    SELECT 
     SubDepartment.TaskID, 
     SubDepartment.[Subject], 
     SubDepartment.ParentID ,
     SubDepartment.IsProject,
     HLevel + 1
    FROM 
     Task SubDepartment
    INNER JOIN 
     Hierarchy ParentDepartment
    ON 
     SubDepartment.TaskID = ParentDepartment.ParentID 
)

SELECT 
    TaskID, 
    [Subject], 
    ParentID,
    IsProject,
    HLevel
FROM  
    Hierarchy
ORDER BY
    HLevel DESC

Answer 2

Thanks for posting the solution. I saved a lot of time.