Table: Key Char(15), Parent Char(15), text nVarChar(100)

 1. 
SELECT a.*, b.parent, b.text FROM 
   (select rank=count(*), a1.[key]
   from Yourt_table a1, your_table a2
   where a1.[key] >= a2.[key]
   group by a1.[key]) a
   LEFT JOIN your_table b on a.[key] = b.[key]

2.
SELECT  tree.real_key, tree.parent, tree.text from 
(select key_, key_ AS real_key, parent, text, 1 as xParent from your_table 
	WHERE key_ in (select parent from your_table) 
UNION ALL
select a.key_, b.key_ AS realKey,b.parent, b.text, 2 as xparent from
(select key_, parent, text from your_table 
	WHERE key_ in (select parent from your_table)) a
	LEFT JOIN (select key_, parent, text from your_table) b
	ON a.key_ = b.parent) tree
 ORDER BY cast(replace(tree.key_,'_','') AS int), cast(replace(tree.parent,'_','') AS int), tree.text


3. 
WITH testEnum ( text,[key], parent,  EnumNr, sort )
AS 
(Select text, [key], parent, 1,CONVERT(varchar(8000), [key]) from your_table e WHERE [key] = '5_'
	UNION ALL
Select e.text, e.[key], e.parent,  enumNr + 1,RTRIM(Sort)+ '\'+e.[key] from your_table as e
JOIN testEnum d ON e.[parent] = d.[key]
)
SELECT  REPLICATE('   ', EnumNr)+Text,[key], parent, EnumNr 
FROM testEnum ORDER BY sort
go