SQL Server function to get top level parent in hierarchy - sql

Question

I have following table (master_group) structure :
code name under
1 National Sales Manager 1
2 regional sales manager 1
3 area sales manager 2
4 sales manager 3
How do I get the ultimate parent of a particular row like :
code name under ultimateparent
1 National Sales Manager 1 1
2 regional sales manager 1 1
3 area sales manager 2 1
4 sales manager 3 1

Answer 1

With recursive cte going from top to childs:
with cte as(
select *, code as ultimate from t where code = under
union all
select t.*, c.ultimate from t
join cte c on c.code = t.under
where t.code <> t.under
)
select * from cte
For data:
create table t (code int, name varchar(100), under int)
insert into t values
(1, 'National Sales Manager', 1),
(2, 'regional sales manager', 1),
(3, 'area sales manager', 2),
(4, 'sales manager', 3),
(5, 'a', 5),
(6, 'b', 5),
(7, 'c', 5),
(8, 'd', 7),
(9, 'e', 7),
(10, 'f', 9),
(11, 'g', 9)
it generates the output:
code name under ultimate
1 National Sales Manager 1 1
5 a 5 5
6 b 5 5
7 c 5 5
8 d 7 5
9 e 7 5
10 f 9 5
11 g 9 5
2 regional sales manager 1 1
3 area sales manager 2 1
4 sales manager 3 1
Fiddle http://sqlfiddle.com/#!6/17c12e/1

Answer 2

You can use a recursive CTE to walk the tree and then choose the highest level for each code:
with cte as (
select mg.code, mg.name as name, mg.under as under, mg.under as parent, 1 as lev
from master_group mg
union all
select mg.code, mg.name, mg.under, cte.under as parent, cte.lev + 1
from master_group mg join
cte
on mg.under = cte.code
where cte.under is not null and cte.under <> mg.code
)
select code, name, under, parent as ultimateparent
from (select cte.*, max(lev) over (partition by cte.code) as maxlev
from cte
) t
where lev = maxlev;
Here is a SQL Fiddle.

Answer 3

I would put NULL as under (in my example ParentId) when it's the top record. With this assumption here's a solution
;
WITH Result AS
(
SELECT Id, ParentId, Name, Id as [Top] FROM
sample
where ParentId IS NULL
UNION ALL
SELECT s.Id, s.ParentId, s.Name, [Top]
FROM sample s INNER JOIN Result R ON s.ParentId = R.Id
)
http://sqlfiddle.com/#!6/13b9d/14

Answer 4

I suggest you to use a recursive function like this:
CREATE FUNCTION dbo.parentID (#code int)
RETURNS int AS
BEGIN
DECLARE #ResultVar int
SELECT #ResultVar = (SELECT under FROM master_group WHERE code = #code)
IF #ResultVar <> #code
BEGIN
SELECT #ResultVar = dbo.parentID(#ResultVar)
END
RETURN #ResultVar
END
GO
An use it like this:
SELECT *,
dbo.parentId(code) AS ultimateparent
FROM master_group

Answer 5

I'm going to shamelessly steal the data setup from another answer and demonstrate how you'd do this with hierarchyid:
create table t (code int, name varchar(100), under int)
insert into t values
(1, 'National Sales Manager', null),
(2, 'regional sales manager', 1),
(3, 'area sales manager', 2),
(4, 'sales manager', 3),
(5, 'a', null),
(6, 'b', 5),
(7, 'c', 5),
(8, 'd', 7),
(9, 'e', 7),
(10, 'f', 9),
(11, 'g', 9);
with cte as (
select code, name, under as parentCode, code as ultimateParent, cast('/' + cast(code as varchar) + '/' as nvarchar(max)) as h
from t
where under is null
union all
select child.code, child.name, child.under as ParentCode, parent.ultimateParentCode, cast(parent.h + cast(child.code as varchar) + '/' as nvarchar(max))
from t as child
join cte as parent
on child.under = parent.code
), hier as (
select code, name, parentCode, ultimateParentCode, cast(h as hierarchyid) as h
from cte
)
select code, name, parentCode, ultimateParentCode, h.ToString(), h.GetAncestor(h.GetLevel()-1).ToString()
from hier
Keep in mind, the recursive CTE need only be done once (or on data changes). The point that I'm making is that once you have a hierarchyid calculated (which you can store in row, btw), it's easy to answer the question you're posing with method calls on the hierarchyid (and possibly a join if you want to get back the progenitor's info).