How to create query from parent child hierarchy table

Question

How do I write my query to translate a table with parent / child hierarchy into a table with my hierarchy levels in separate columns?

I have a table in SQL Server (f

Answer 1

If you have a fixed or limited number of levels, you may not need DYNAMIC SQL. "Parsing" the path can be accomplished with a little XML.

Consider the following:

Example:

Declare @YourTable Table ([Parent] varchar(50),[Child] varchar(50))
Insert Into @YourTable Values 
 (null ,'S-1')
,('S-1','S-11')
,('S-1','S-12')
,('S-1','S-13')
,('S-1','S-14')
,('S-1','S-15')
,('S-11','S-111')
,('S-11','S-112')

;with cteP as (
      Select Child
            ,Parent 
            ,PathID = cast(Child as varchar(500))
      From   @YourTable
      Where  Parent is Null
      Union  All
      Select Child  = r.Child
            ,Parent = r.Parent 
            ,PathID = cast(p.PathID+','+cast(r.Child as varchar(25)) as varchar(500))
      From   @YourTable r
      Join   cteP p on r.Parent  = p.Child)
Select [Group] = Child
      ,B.*
 From  cteP A
 Cross Apply (
                Select Level1 = xDim.value('/x[1]','varchar(max)')
                      ,Level2 = xDim.value('/x[2]','varchar(max)')
                      ,Level3 = xDim.value('/x[3]','varchar(max)')
                      ,Level4 = xDim.value('/x[4]','varchar(max)')
                      ,Level5 = xDim.value('/x[5]','varchar(max)')
                From  (Select Cast('<x>' + replace(PathID,',','</x><x>')+'</x>' as xml) as xDim) as X 
             ) B
  Order By PathID

Returns