SQL - Recursively finding count in another table - sql

Question

I have a table which has both category and subcategory such as this :
CategoryID CategoryName ParentCategoryID
1 CatA NULL
2 CatA1 1
3 CatA2 1
4 CatA3 1
5 CatB NULL
6 CatB1 5
7 CatC NULL
8 CatC1 7
I have another table where I have mappings
MappingID CategoryID ItemID
1 2 1
2 3 1
3 6 2
4 8 3
5 2 3
6 3 4
7 4 4
8 2 3
9 3 4
10 2 2
11 2 2
12 2 2
13 2 3
14 2 1
I need a result set where count of all items per category is displayed such as :
Category No. of Items
1 12
5 1
7 1
Could you someone guide me with this?
I have tried using a CTE :
WITH CTE (CategoryID, CategoryName, ParentID, CategoryParentName)
AS
(
SELECT CategoryID,
CategoryName,
ParentCategoryID,
CategoryName AS CategoryParentName
FROM [dbo].[Category]
WHERE ParentCategoryID IS NULL
AND IsDeleted = 0
UNION ALL
SELECT garages.CategoryID,
garages.CategoryName,
garages.ParentCategoryID,
traces.CategoryName AS CategoryParentName
FROM [dbo].[Category] AS garages
INNER JOIN CTE AS traces ON traces.CategoryID= garages.ParentCategoryID
)
SELECT gr.CategoryID, COUNT(map.CategoryID) AS Total
FROM CTE gr
INNER JOIN [dbo].[CategoryMapping] map ON gr.CategoryID = map.CategoryID
GROUP BY gr.CategoryID

Answer 1

If there are just two levels of categories than there is no need for recursive query
select coalesce(c.ParentCategoryID, c.CategoryID), count(*)
from Category c
join CategoryMapping m on c.CategoryID = m.CategoryID
group by coalesce(c.ParentCategoryID, c.CategoryID)
Obviously, categories without mapping won't be there.