Calculating Formula with CTE tree - sql

Question

Data
I have following partial data
id parent multiplier const
-- ------ ---------- -----
1 NULL 1.10 1.00
2 1 1.20 2.00
3 1 1.30 3.00
4 1 2.40 4.00
5 2 2.50 5.00
6 2 2.60 6.00
7 2 2.70 17.00
8 3 2.80 18.00
9 3 3.90 19.00
10 3 3.10 7.00
11 8 3.20 8.00
12 8 3.30 9.00
13 8 3.40 10.00
14 9 4.50 11.00
15 10 4.60 21.00
15 10 4.70 22.00
Which can be displayed in a tree as following
1
+-- 2
| +-- 5
| +-- 6
| +-- 7
|
+-- 3
| +-- 8
| | +-- 11
| | +-- 12
| | +-- 13
| |
| +-- 9
| | +-- 14
| |
| +-- 10
| +-- 15
| +-- 16
|
+-- 4
SQL to create the table structure and data
DECLARE #table TABLE (Id int, Parent int, multiplier decimal(6,3), Const decimal(6,3));
INSERT INTO #table
SELECT 1, NULL, 1.1, 1.00 UNION
SELECT 2, 1, 1.2, 2.00 UNION
SELECT 3, 1, 1.3, 3.00 UNION
SELECT 4, 1, 2.4, 4.00 UNION
SELECT 5, 2, 2.5, 5.00 UNION
SELECT 6, 2, 2.6, 6.00 UNION
SELECT 7, 2, 2.7, 17.00 UNION
SELECT 8, 3, 2.8, 18.00 UNION
SELECT 9, 3, 3.9, 19.00 UNION
SELECT 10, 3, 3.1, 7.00 UNION
SELECT 11, 8, 3.2, 8.00 UNION
SELECT 12, 8, 3.3, 9.00 UNION
SELECT 13, 8, 3.4, 10.00 UNION
SELECT 14, 9, 4.5, 11.00 UNION
SELECT 15, 10, 4.6, 21.00 UNION
SELECT 15, 10, 4.7, 22.00;
Problem
I need to calculate recursive aX+b formula up to the root for any node in the tree. In other words I need to calculate the formula for child node and move resulting value up to parent as x and continue calculation until I reach root.
For example calculating x=1250.00 for node 14 will be
1.10 * (1.30 *( 3.90 * (4.50 * 1250.00 + 11.00) + 19.00) + 3.00) + 1.00 = 31463.442
Currently I am doing this using CTE tree and a C# however I am not satisfied with its speed and optimization.
Question
Can I do this calculation on SQL server and just return the value? If it is possible, what is the tree depth that I can navigate with CTE?

Answer 1

Can I do this calculation on SQL server and just return the value?
Yes, do the recursion from the leaf node, do the calculation as you go and get the max value in the main query.
with C as
(
select T.Id,
T.Parent,
cast(T.multiplier * #x + T.Const as decimal(19, 3)) as x
from #table as T
where T.Id = 14
union all
select T.Id,
T.Parent,
cast(T.multiplier * C.x + T.Const as decimal(19, 3))
from C
inner join #table as T
on C.Parent = T.Id
)
select max(C.x) as Value
from C
option (maxrecursion 0);
If it is possible, what is the tree depth that I can navigate with
CTE?
Default is 100 but you can change that with maxrecursion. When using option (maxrecursion 0) there is no limit.
I am not satisfied with its speed and optimization.
To fix that you have to show what you actually do. The sample you have provided gets a good plan if you have a clustered primary key on Id.
It does a seek to find the anchor and seeks for each iteration.