Count Childs and partition by GrandParent, that resides in an unpivoted hierarchy - sql

Question

I want to show the COUNT on every row how many BuildingID's there are within the MainGroundID's, while having to deal with a parent-child hierarchy that is unpivoted.
Unfortunately there is no logic within the way the GroundID and MainGroundID's are written (although it looks that way in my example, since I made an example dataset).
PMEBuilding
BuildingID, GroundID
1, 100
2, 100
3, 101
4, 201
5, 201
6, 201
7, 202
In reality the above table has 34K rows and 80+ fields.
The GroundID from the table above is N:1 to the table below via GroundID.
Within the PMEGroudn table Some GroundID's refer to a certain MainGroundID, which in turn also refer to Parents higher up in the hierarchy. The 'GrandParents' are those that have a NULL value as GroundID.
PMEGround
GroundID, MainGroundID
1, NULL --GrandParent
10, 1
100, 10
101, 10
2, NULL --GrandParent
20, 2
201, 20
202, 20
In reality the above table has 2K rows of which around 500 'GrandParents'.
I want this to be the end result:
MainGroundID MainGroundBuildingCount
1, 3
2, 7
The following code is what I used so far, but it doesn't work entirely yet:
;WITH UNPIVOT_HIERARCHY AS (
SELECT GROUNDID
,MAINGROUNDID
,PathID = CAST(GROUNDID AS VARCHAR(MAX))
FROM PMEGROUND
WHERE NULLIF(MainGroundID, '') IS NULL
UNION All
SELECT GROUNDID = r.GROUNDID
,MAINGROUNDID = r.MAINGROUNDID
,PathID = p.PathID+CONCAT(',',CAST(r.GROUNDID AS VARCHAR(MAX)))
FROM PMEGROUND r
JOIN UNPIVOT_HIERARCHY p ON r.MAINGROUNDID = p.GROUNDID
)
SELECT
B.Lvl3 AS 'MainGroundID' --This is the GrandParent, which works fine
,COUNT(PMEBUILDING.GROUNDID) OVER (PARTITION BY B.Lvl3) AS 'MainGroundCountBuildings'
FROM PMEGROUND
LEFT JOIN UNPIVOT_HIERARCHY
ON UNPIVOT_HIERARCHY.GROUNDID = PMEGROUND.GROUNDID
LEFT JOIN PMEBUILDING
ON PMEBUILDING.GROUNDID = PMEGROUND.GROUNDID
CROSS Apply (
SELECT Lvl1 = xDim.value('/x[3]','varchar(50)')
,Lvl2 = xDim.value('/x[2]','varchar(50)')
,Lvl3 = xDim.value('/x[1]','varchar(50)')
,Lvl4 = xDim.value('/x[4]','varchar(50)')
FROM ( VALUES (CAST('<x>' + REPLACE(PathID,',','</x><x>')+'</x>' AS xml))) B(xDim)
) B
GROUP BY B.Lvl3, PMEBUILDING.GROUNDID
Without the GROUP BY it gives duplicate MainGroundIDs, but the correct count.
With the GROUP BY it still gives duplicate MainGroundIDs but less, but the count is messed up now.

Answer 1

I want this to be the end result:
MainGroundID MainGroundBuildingCount
1, 3
2, 7
Don't you mean the end result should be?
MainGroundID MainGroundBuildingCount
1, 3
2, 4
Assuming, based on the given data, that there are 3 levels of hierarchy and PMEBuilding.GroundID contains only grandchildren I would use the following to achieve the end result:
select
gp.GroundID, count(distinct b.BuildingID)
from PMEGround gp
join PMEGround p on p.MainGroundID = gp.GRoundID
join PMEGround c on c.MainGroundID = p.GRoundID
join PMEBuilding b on b.GroundID = c.GroundID
where gp.MainGroundID is null
group by gp.GroundID
order by 1