Tree Node Calculation - SQL Server

I'd appreciate some help with something I am trying to achieve please.

The parts that my company make are built from sub assemblies and sub assemblies of sub assemblies.
This looks like:

1
         /   \  \
        /     |   \
       2      3    7
      / \    / \
     4   5  4   6

Where 4 & 5 come together to make 2, 4 & 6 make 3, then assemblies 2, 3 & 7 make 1.

My table looks like this;

+------+-----+-------+----------+----------------+
| ROOT | SUB | LEVEL | LEADTIME | TOP LEVEL PART |
+------+-----+-------+----------+----------------+
|    1 |   1 |     0 |        4 |              1 |
|    1 |   2 |     1 |        2 |              1 |
|    1 |   3 |     1 |        5 |              1 |
|    1 |   7 |     1 |       20 |              1 |
|    2 |   4 |     1 |        4 |              1 |
|    2 |   5 |     1 |        1 |              1 |
|    3 |   4 |     2 |        4 |              1 |
|    3 |   6 |     2 |        5 |              1 |
+------+-----+-------+----------+----------------+

Each part has a lead time of how long it takes to make it. What I want to do is pass a top level part number and it calculate the overall lead time for the part.

Originally I thought I could just group by the Level and take the maximum lead time per level and add them together but that wouldn't be accurate. Level 1 Part 7 takes 20 days to make so we would be able to be making all of the other parts whilst 7 was being made. The calculation needs to be based on the part that consumes its parent (for want of a better phrase).

What I need to do is calculate the lead time for every route through the tree and add up the lead times as it goes. So I would like to return a table something like;

```
+----+----------------+-------------------------+------+------------+
| ID | Top Level Part | Parts Nodes Combination | Days | [BASED ON] |
+----+----------------+-------------------------+------+------------+
| 1 | 1 | 1 >> 2 >> 4 | 10 |

This solution also gets the intermediate nodes

;WITH RecursiveCTE
AS
(
SELECT  [SUB] , 
        [SUB] as [Top Level Part],
        CAST([SUB] as varchar(255)) as [Parts Nodes Combination],
        0 AS [LEVEL],
        [LEADTIME]  as [Days],
        CAST([LEADTIME] as varchar(255)) as [BASED ON]
FROM dbo.Levels s1
WHERE [LEVEL] = 0

UNION ALL

SELECT  s1.SUB as [Top Level Part],
        RecursiveCTE.[Top Level Part],
        CAST(RecursiveCTE.[Parts Nodes Combination]+ ' >> ' + cast(s1.[SUB] as varchar(255)) as varchar(255)),
        RecursiveCTE.[LEVEL] + 1 as [LEVEL],
        RecursiveCTE.[Days] + s1.[LEADTIME] as [Days],
        CAST(RecursiveCTE.[BASED ON] + ' + ' + CAST(s1.[LEADTIME] as varchar(255))  as  varchar(255))
FROM dbo.Levels s1
INNER JOIN RecursiveCTE 
ON s1.[ROOT] = RecursiveCTE.[SUB]
WHERE s1.[LEVEL] > 0
)
SELECT * FROM RecursiveCTE
WHERE [LEVEL] != 0;

Result

SUB Top Level Part  Parts Nodes Combination LEVEL   Days    BASED ON
2       1               1 >> 2                  1       6       4 + 2
3       1               1 >> 3                  1       9       4 + 5
7       1               1 >> 7                  1       24      4 + 20
4       1               1 >> 3 >> 4             2       13      4 + 5 + 4
6       1               1 >> 3 >> 6             2       14      4 + 5 + 5
4       1               1 >> 2 >> 4             2       10      4 + 2 + 4
5       1               1 >> 2 >> 5             2       7       4 + 2 + 1

DB<>Fiddle

If you want to filter out the intermediate nodes:

;WITH RecursiveCTE
AS
(
SELECT  [SUB] , 
        [SUB] as [Top Level Part],
        CAST([SUB] as varchar(255)) as [Parts Nodes Combination],
        0 AS [LEVEL],
        [LEADTIME]  as [Days],
        CAST([LEADTIME] as varchar(255)) as [BASED ON]
FROM dbo.Levels s1
WHERE [LEVEL] = 0

UNION ALL

SELECT  s1.SUB as [Top Level Part],
        RecursiveCTE.[Top Level Part],
        CAST(RecursiveCTE.[Parts Nodes Combination]+ ' >> ' + cast(s1.[SUB] as varchar(255)) as varchar(255)),
        RecursiveCTE.[LEVEL] + 1 as [LEVEL],
        RecursiveCTE.[Days] + s1.[LEADTIME] as [Days],
        CAST(RecursiveCTE.[BASED ON] + ' + ' + CAST(s1.[LEADTIME] as varchar(255))  as  varchar(255))
FROM dbo.Levels s1
INNER JOIN RecursiveCTE 
ON s1.[ROOT] = RecursiveCTE.[SUB]

WHERE s1.[LEVEL] > 0

)

SELECT * FROM RecursiveCTE
WHERE [LEVEL] != 0
AND NOT EXISTS 
(
SELECT * FROM
dbo.Levels s2
WHERE RecursiveCTE.SUB = s2.[ROOT])
;

Result

SUB Top Level Part  Parts Nodes Combination LEVEL   Days    BASED ON
7           1               1 >> 7           1      24      4 + 20
4           1               1 >> 3 >> 4      2      13      4 + 5 + 4
6           1               1 >> 3 >> 6      2      14      4 + 5 + 5
4           1               1 >> 2 >> 4      2      10      4 + 2 + 4
5           1               1 >> 2 >> 5      2      7       4 + 2 + 1

DB<>Fiddle

Table & Data used

CREATE TABLE dbo.Levels ([PARTID] INT,[ROOT] int,[SUB] int,[LEVEL] int, [LEADTIME] int,[TOP LEVEL PART] int);
--PartID added
INSERT INTO dbo.Levels
 ([PARTID], [ROOT] ,[SUB] ,[LEVEL] , [LEADTIME] ,[TOP LEVEL PART])

VALUES
(1,1 , 1 ,0 ,4 ,1 ),
(1,1 , 2 ,1 ,2 ,1 ),
(1,1 , 3 ,1 ,5 ,1 ),
(1,1 , 7 ,1 ,20 ,1 ),
(1,2 , 4 ,1 ,4 ,1 ),
(1,2 , 5 ,1 ,1 ,1 ),
(1,3 , 4 ,2 ,4 ,1 ),
(1,3 , 6 ,2 ,5 ,1 );

Edit

Op comments:


I've noticed the data is repeating a lot (particularly on larger
assemblies)


Basically I have Sub Router 1691, on top level router 1731. the Parts
node combination is 1731 -- 1727 -- 1691 and this repeats exactly the
same columns 8 times. Then, when it introduces another node (so 1731
-- 1727 -- 1691 -- 1682), this one repeats 168 times. This is the case all of the way through. It appears that any 3 level nodes repeat 8
times & any 4 level nodes 168 times.


On a different one it repeats far fewer times. I'm wondering whether
it has something to do with the number of unique parts in the tree.


I think I've figured it out! A single sub can appear on several
different top level parts. On the join to the recursiveCTE table I've
also added 'and RecursiveCTE.[Top Level Part] = s1.TopLevelRouter' and
I think it's done the trick.

Part of the query that needed to be changed:

...    
FROM dbo.Levels s1
INNER JOIN RecursiveCTE 
ON s1.[ROOT] = RecursiveCTE.[SUB]
and RecursiveCTE.[Top Level Part] = s1.TopLevelRouter
WHERE s1.[LEVEL] > 0
)
SELECT * FROM RecursiveCTE
WHERE [LEVEL] != 0;

StackExchange Database Administrators Q#242653, answer score: 3