How to calculate the sum of values in a tree using SQL

ID    ParentID    Points
1     0           230
2     1           150
3     0           80
4     1           110
5     4           54
6     4           342

Tree:
0
|---
1    3
|
2  4---

     5  6

ID    Points    Level1     Level2
1     230       150+110    150+110+54+342
2     150
3     80
4     110       54+342
5     54
6     342

SELECT rel.parent_id, SUM(tbl.points)
FROM table tbl INNER JOIN relations rel ON tbl.id=rel.id
WHERE rel.parent_id <> 0
GROUP BY rel.parent_id;

WITH Parent (id, GrandParentId, parentId, Points, Level1Points, Level2Points)
AS
(
    -- Find root
    SELECT id,
    		0 AS GrandParentId,
    		ParentId,
    		Points,
    		0 AS Level1Points,
    		0 AS Level2Points
    FROM tblPoints ptr
    WHERE ptr.ParentId = 0

    UNION ALL (
    -- Level2 Points
    SELECT pa.GrandParentId AS Id,
    		NULL AS GrandParentId,
    		NULL AS ParentId,
    		0 AS Points,
    		0 AS Level1Points,
    		pa.Points  AS Level2Points
    FROM tblPoints pt
    		JOIN Parent pa ON pa.GrandParentId = pt.Id
    UNION  ALL
    -- Level1 Points
    SELECT pt.ParentId AS Id,
    		NULL AS GrandParentId,
    		NULL AS ParentId,
    		0 AS Points,
    		pt.Points AS Level1Points,
    		0 AS Level2Points
    FROM tblPoints pt
    		JOIN Parent pa ON pa.Id = pt.ParentId AND pa.ParentId IS NOT NULL
    UNION  ALL
    -- Points
    SELECT pt.id,
    		pa.ParentId AS GrandParentId,
    		pt.ParentId,
    		pt.Points,
    		0 AS Level1Points,
    		0 AS Level2Points
    FROM tblPoints pt
    		JOIN Parent pa ON pa.Id = pt.ParentId AND pa.ParentId IS NOT NULL )
)
SELECT id,
    SUM(Points) AS Points,
    SUM(Level1Points) AS Level1Points,
    CASE WHEN SUM(Level2Points) > 0 THEN  SUM(Level1Points) + SUM(Level2Points) ELSE 0 END AS Level2Points
FROM Parent
GROUP BY id
ORDER by id

CREATE FUNCTION CALC
(
@node integer,
)
returns
(
@total integer
)
as
begin
    select @total = (select node_value from yourtable where node_id = @node);

    declare @children table (value integer);
    insert into @children
    select calc(node_id) from yourtable where parent_id = @node;

    @current = @current + select sum(value) from @children;
    return
end

Id   ParentId
1   NULL
11    1
12    1
110 11
111 11
112 11
120 12
121 12
122 12
123 12
124 12

Id     Val
110 500
111 50
112 5
120 3000
121 30000
122 300000

;WITH Data (Id, Val) AS
(
    select t.Id, SUM(v.val) as Val from dbo.TestTable t
    join dbo.Amount v on t.Id = v.Id
    group by t.Id
)

select cd.Id, ISNULL(SUM(cd.Val), 0) as Amount FROM
(
    -- level 3
    select t.Id, d.val from TestTable t
    left join Data d on d.id = t.Id

    UNION

    -- level 2
    select t.parentId as Id, sum(y.Val) from TestTable t
    left join Data y on y.id = t.Id
    where t.parentId is not null
    group by t.parentId

    UNION

    -- level 1
    select t.parentId as Id, sum(y.Val) from TestTable t
    join TestTable c on c.parentId = t.Id
    left join Data y on y.id = c.Id
    where t.parentId is not null
    group by t.parentId
) AS cd
group by id

Id     Amount
1     333555
11   555
12   333000
110 500
111 50
112 5
120 3000
121 30000
122 300000
123 0
124 0