How can I generate a hierarchy path in SQL that leads to a given node?

Question

In my MS SQL 2008 R2 database I have this table:

TABLE [Hierarchy]
[ParentCategoryId] [uniqueidentifier] NULL,
[ChildCategoryId] [uniqueidentifier] NOT NULL         


        

Answer 1

That's an interesting hierarchy structure. Seems to allow for parents to possibly be children of their children. If this were to happen this code logic would break, but as long as that doesn't occur this should work.

Create  Function dbo.IdentifyHierarchyPaths (@DeepestChildNode UniqueIdentifier)
Returns @hierarchy Table
(
        Hierarchy Varchar(Max)
)
As
Begin
        ;With   BuildHier As
        (
                Select  Convert(Varchar(Max),h2.ChildCategoryId) As child, Convert(Varchar(Max),h1.ChildCategoryId) + ' > ' +  Convert(Varchar(Max),h2.ChildCategoryId) As hier
                From    Hierarchy h1
                Left    Join Hierarchy h2
                        On  h1.ChildCategoryId = h2.ParentCategoryId
                Where   h1.ParentCategoryId Is Null
                Union   All
                Select  Convert(Varchar(Max),h1.ChildCategoryId) As child, bh.hier + ' > ' +  Convert(Varchar(Max),h1.ChildCategoryId) As hier
                From    BuildHier bh
                Join    Hierarchy h1
                        On  bh.child = h1.ParentCategoryId
        ),      HierWithTopLevel As
        (
                Select  Convert(Varchar(Max),ChildCategoryId) As hierarchy
                From    Hierarchy
                Where   ParentCategoryId Is Null
                Union   
                Select  hier
                From    BuildHier
        )
        Insert  @hierarchy
        Select  hierarchy
        From    HierWithTopLevel
        Where   Right(hierarchy,36) = Convert(Varchar(36),@DeepestChildNode);
        Return;
End;