Get total number of parents - sql-server

Question

I am upgrading a legacy application and I need to find the number of parents certain rows in a table have.
I was thinking of using a declared procedure for this, but i'm having trouble figuring it out how to make it work.
Basically you have a table with id and parent
= id = parent =
= 0 = 0 =
= 1 = 0 =
= 2 = 1 =
= 3 = 1 =
= 4 = 2 =
ID is unique, and parent is variable depending on what was used to create that entry, but it will always match a row with matching ID
What i'd like to achieve is calling one procedure that returns all matching parent numbers as a simple iterable result set.
So if i were to do getAllParents(4) it should return me 2, 1, 0
My failed attempts at looping have brought me so far
CREATE PROCEDURE getNumberOfParents #start int #current int
as
begin
SELECT parent FROM test where id=#start
if(parent > 0)
begin
set #current = #current + 1;
set #current = #current + getNumberOfParents(parent,#current);
end
end
Due to restrictions I cannot use an extra table to achieve this, otherwise i'd be easy heh. i can however make temptables that can be cleaned up after the method exits.

Answer 1

You can do it without a while loop by the use of a recursive CTE:
DECLARE #lookupId INT = 4
;WITH ParentsCTE AS (
SELECT id, parent
FROM #mytable
WHERE id = #lookupId
UNION ALL
SELECT m.id, m.parent
FROM #mytable AS m
INNER JOIN ParentsCTE AS p ON m.id = p.parent
WHERE m.id <> m.parent
)
SELECT parent
FROM ParentsCTE
The anchor member of the above CTE:
SELECT id, parent
FROM #mytable
WHERE id = #lookupId
returns the immediate parent of the 'lookup id'.
The recursive member:
SELECT m.id, m.parent
FROM #mytable AS m
INNER JOIN ParentsCTE AS p ON m.id = p.parent
WHERE m.id <> m.parent
keeps adding parents up the hierarchy until a root node (m.id <> m.parent predicate detects this) has been reached.
SQL Fiddle Demo

Answer 2

Test Data
DECLARE #Table TABLE (id INT, parent INT)
INSERT INTO #Table VALUES
(0 , 0),
(1 , 0),
(2 , 1),
(3 , 1),
(4 , 2)
Query
-- Id you want all the parents for
DECLARE #ParentsFor INT = 4
;with parents as
(
select ID, parent
from #Table
where parent IS NOT NULL
union all
select p.ID, t.parent
from parents p
inner join #Table t on p.parent = t.ID
and t.ID <> t.parent
)
select Distinct
STUFF((SELECT ',' + Cast(parent AS VarChar(10))
FROM parents
WHERE ID = #ParentsFor
FOR XML PATH(''),TYPE).value('.','NVARCHAR(MAX)'),1,1,'')
FROM parents
Result
2,1,0
SQL FIDDLE

Answer 3

Fiddle Demo Here
try:
declare #id varchar(max)=''
declare #getid int=4
while #getid>0
begin
select #id=#id+cast(parent as varchar(10))+',' from tab_1
where id=#getid
select #getid=parent from tab_1 where id=#getid
end
select #id

Answer 4

Try to use while loop as presented in this example:
http://blog.sqlauthority.com/2007/10/24/sql-server-simple-example-of-while-loop-with-continue-and-break-keywords/