Filtering out hierarchical data - tsql

Question

I need help with a problem I am facing processing hierarchical data.
Schema of the tables that maintain hierarchical data:
Category table:
| ID | Label |
Mapping table:
| ID | QualifierID | ItemID | ParentID |
Step 1: Wrote a simple self-join query to trasnform above mappings:
WITH category_masterlist AS (
SELECT id,
label
FROM Category
)
select id, id as itemid, label, NULL as parentId from [Category] where categoryLevel = 1
UNION
select itemid as id, itemId, (select label from category_masterlist where id = cm.itemid) Label, parentId
from [CategoryMapping] cm
Step 2: Wrote a self-join query using common table expression to return mapping data as follows:
WITH CategoryCTE(ParentID, ID, Label, CategoryLevel) AS
(
SELECT ParentID, ItemID, Label, 0 AS CategoryLevel
FROM [view_TreeviewCategoryMapping]
WHERE ParentID IS NULL
UNION ALL
SELECT e.ParentID, e.ItemID, e.Label, CategoryLevel + 1
FROM [view_TreeviewCategoryMapping] AS e
INNER JOIN CategoryCTE AS d
ON e.ParentID = d.ID
)
SELECT distinct ParentID, ID, Label, CategoryLevel
FROM CategoryCTE
| ID | Label | ParentID | CategoryLevel |
--------------------------------------------------------------------------------
| 90 | Satellite | NULL | 0 |
| 91 | Concrete | NULL | 0 |
| 92 | ETC | NULL | 0 |
| 93 | Chisel | NULL | 0 |
| 94 | Steel | NULL | 0 |
| 96 | Wood | NULL | 0 |
| 97 | MIC Systems | 90 | 1 |
| 97 | MIC Systems | 91 | 1 |
| 99 | Foundations | 91 | 1 |
| 100 | Down Systems | 91 | 1 |
| 101 | Side Systems | 91 | 1 |
| 102 | Systems | 91 | 1 |
| 98 | DWG | 92 | 1 |
| 97 | MIC Systems | 93 | 1 |
| 97 | MIC Systems | 94 | 1 |
| 99 | Foundations | 94 | 1 |
| 100 | Down Systems | 94 | 1 |
| 101 | Side Systems | 94 | 1 |
| 102 | Systems | 94 | 1 |
| 97 | MIC Systems | 95 | 1 |
| 98 | DWG | 95 | 1 |
| 102 | Systems | 95 | 1 |
| 103 | Project Management| 95 | 1 |
| 104 | Software | 95 | 1 |
| 99 | Foundations | 96 | 1 |
| 119 | Fronts | 97 | 2 |
| 121 | Technology | 98 | 2 |
| 112 | Root Systems | 98 | 2 |
| 112 | Root Systems | 99 | 2 |
| 137 | Closed Systems | 112 | 3 |
| 203 | Support | 121 | 3 |
Step 3: I would like to filter above results so that only categories that are mapped completely are returned. Completed mapping is a mapping that has children at level=3. For example, below is what I am looking for based on above resultset:
| ID | Label | ParentID | CategoryLevel |
--------------------------------------------------------------------------------
| 96 | Wood | NULL | 0 |
| 92 | ETC | NULL | 0 |
| 98 | DWG | 92 | 1 |
| 99 | Foundations | 96 | 1 |
| 121 | Technology | 98 | 2 |
| 112 | Root Systems | 98 | 2 |
| 112 | Root Systems | 99 | 2 |
| 137 | Closed Systems | 112 | 3 |
| 203 | Support | 121 | 3 |
Step 4: Ultimately, end user should be presented with a tree view control as follows:
Root
|
|---Wood
| |---Foundations
| |---Root Systems
| |---Closed Systems
|
|---ETC
| |---DWG
| |---Technology
| |---Support
| |---Root Systems
| |---Closed Systems
Please note, a category can have multiple parents. For example, Root Systems has two parents - DWG and Foundations. Did I get the schema correct for category and mapping table especially for the case when a category can have multiple parents?
How can I filter out categories that are not mapped completely from Step 2 to Step 3? That is the hurdle I am unable to cross. Any pointers? I can filter them out at the application level but would really love to filter them out at database level.
I am open to suggestions and recommendations that will help me achieve my goal. I also want a confirmation that the schema I am using is the most efficient one.
Thank you!

Answer 1

Here is a working option that uses the datatype hierarchyID
The nesting is option and really for illustration.
Example
Declare #Top int = null --<< Sets top of Hier Try 94
;with cteP as (
Select ID
,ParentID
,Label
,HierID = convert(hierarchyid,concat('/',ID,'/'))
From YourTable
Where IsNull(#Top,-1) = case when #Top is null then isnull(ParentID ,-1) else ID end
Union All
Select ID = r.ID
,Pt = r.ParentID
,Label = r.Label
,HierID = convert(hierarchyid,concat(p.HierID.ToString(),r.ID,'/'))
From YourTable r
Join cteP p on r.ParentID = p.ID)
Select Lvl = HierID.GetLevel()
,ID
,ParentID
,Label = replicate('|----',HierID.GetLevel()-1) + Label -- Nesting Optional ... For Presentation
,HierID_String = HierID.ToString()
From cteP A
Order By A.HierID
Results
Now if #Top was set to 94