TSQL - Mapping Parent/Child Hierarchy - sql

Question

Sample Data:
DECLARE #Hierarchy TABLE
(
[ParentId] INT
, [ChildId] INT
) ;
INSERT INTO #Hierarchy
VALUES
( 1, 2 )
, ( 1, 3 )
, ( 2, 4 )
, ( 3, 5 )
, ( 4, 3 )
, ( 4, 6 )
, ( 5, 6 )
, ( 7, 3 ) ;
Current Query:
; WITH CTE AS
(
SELECT [ParentId]
, [ChildId]
, 1 AS [Level]
, CONCAT ( CAST ( [ParentId] AS VARCHAR(MAX) ), '.', CAST ( [ChildId] AS VARCHAR(MAX) ) ) AS [Path]
FROM #Hierarchy
UNION ALL
SELECT [C].[ParentId]
, [T].[ChildId]
, [C].[Level] + 1
, CAST ( [C].[Path] + '.' + CAST([T].[ChildId] AS VARCHAR(MAX) ) AS VARCHAR(MAX) )
FROM CTE AS [C]
JOIN #Hierarchy AS [T]
ON [C].[ChildId] = [T].[ParentId]
)
SELECT *
FROM CTE
ORDER BY [ParentId]
, [Level]
, [ChildId] ;
Goal:
distinctly group levels of shared "path" together
find the shallowest and the deepest levels of the shared "path"
Expected Output:
NOTICE: the records with Orange highlight at the end are manually inserted to show what I'm expecting, but haven't figure out yet.
Group: Basically a "dense rank" of each "groups" of nodes that follow the same path. I think if you look at the values of Group in the above image and relate it to Level and Path field's data, it'll make more sense.
IsShallowest: 1st level (I can see that now that someone brought it up). Just need to figure out how to derive those missing (repeating) records
IsDeepest: max level within the group.
Think IsShallowest and IsDeepest is easy to figure out once "Group" logic is figured out and adding missing (repeated) records.

Answer 1

Please check this solution. It provide the requested solution except adding the extra row which more information is needed
;WITH CTE AS (
SELECT
[ParentId]
, [ChildId]
, 1 AS [Level]
, CONCAT ( CAST ( [ParentId] AS VARCHAR(MAX) ), '.', CAST ( [ChildId] AS VARCHAR(MAX) ) ) AS [Path]
, MyGroup1 = ROW_NUMBER() OVER(ORDER BY [ParentId])
, MyGroup2 = ROW_NUMBER() OVER(ORDER BY [ParentId])
FROM Hierarchy
UNION ALL
SELECT
[C].[ParentId]
, [T].[ChildId]
, [C].[Level] + 1
, CAST ( [C].[Path] + '.' + CAST([T].[ChildId] AS VARCHAR(MAX) ) AS VARCHAR(MAX) )
, MyGroup1 = C.MyGroup1
, MyGroup2 = [C].[MyGroup1] + ROW_NUMBER() OVER(ORDER BY [T].[ParentId]) - 1
FROM CTE AS [C]
JOIN Hierarchy AS [T] ON [C].[ChildId] = [T].[ParentId]
)
, MyCTE2 as (
SELECT
[ParentId]
, [ChildId]
, [Level]
, [Path]
-- un-comment bellow 2 rows to see the logic
--, MyGroup1
--, MyGroup2
, MyGroup = DENSE_RANK() OVER (ORDER BY MyGroup1, MyGroup2)
FROM CTE
),
MyCTE3 as (
SELECT
[ParentId]
, [ChildId]
, [Level]
, [Path]
, MyGroup
, shallowest = ROW_NUMBER() OVER(PARTITION BY MyGroup ORDER BY [Path])
, deepest = ROW_NUMBER() OVER(PARTITION BY MyGroup ORDER BY [Path] DESC)
FROM MyCTE2
)
SELECT
[ParentId]
, [ChildId]
, [Level]
, [Path]
, MyGroup
, ISshallowest = CASE WHEN shallowest = 1 then 1 else 0 END
, Isdeepest = CASE WHEN deepest = 1 then 1 else 0 END
FROM MyCTE3
ORDER BY
--[Path]
[ParentId]
, [Level]
, [ChildId];