Recursive query SQL Server not working as expected - sql-server

Question

thanks in advance for you help. I'm still quite new to MS SQL db but I was wondering why my recursive query for MSSQL below does not return the value i'm expecting. I've done my research and at the bottom is the code I came up with. Lets say I have the following table...
CategoryID ParentID SomeName
1 0 hmm
2 0 err
3 0 woo
4 3 ppp
5 4 ttt
I'm expecting the query below to return 3 4 5. I basically wanted to get the list of category id's heirarchy below it self inclusive based on the category id I pass in the recursive query. Thanks for you assistance.
GO
WITH RecursiveQuery (CategoryID)
AS
(
-- Anchor member definition
SELECT a.CategoryID
FROM [SomeDB].[dbo].[SomeTable] AS a
WHERE a.ParentID = CategoryID
UNION ALL
-- Recursive member definition
SELECT b.CategoryID
FROM [SomeDB].[dbo].[SomeTable] AS b
INNER JOIN RecursiveQuery AS d
ON d.CategoryID = b.ParentID
)
-- Statement that executes the CTE
SELECT o.CategoryID
FROM [SomeDB].[dbo].[SomeTable] AS o
INNER JOIN RecursiveQuery AS d
ON d.CategoryID = 3
GO

Answer 1

If you want tree from specific root:
DECLARE #rootCatID int = 3
;WITH LessonsTree (CatID)
AS
(
SELECT a.CategoryID
FROM [EducationDatabase].[dbo].[LessonCategory] AS a
WHERE a.CategoryID = #rootCatID ---<<<
UNION ALL
SELECT b.CategoryID
FROM LessonsTree as t
INNER JOIN [EducationDatabase].[dbo].[LessonCategory] AS b
ON b.ParentID = t.CatID
)
SELECT o.*
FROM LessonsTree t
INNER JOIN [EducationDatabase].[dbo].[LessonCategory] AS o
ON o.CategoryID = t.CatID

Answer 2

As stated in the comments, the anchor isn't restricted. Easiest solution is to add the criterium in the anchor
with RecursiveQuery (theID)
AS
(
SELECT a.ParentID --root id=parentid to include it and to prevent an extra trip to LessonCategory afterwards
FROM [LessonCategory] AS a
WHERE a.ParentID = 3 --restriction here
UNION ALL
SELECT b.CategoryID
FROM [LessonCategory] AS b
INNER JOIN RecursiveQuery AS d
ON d.theID = b.ParentID
)
SELECT* from RecursiveQuery
Another option is to have the recursive query be general (no restricted anchor) and have it keep the rootid as well. Then the query on the cte can restrict on the rootid (the first option is probably better, this second one is mainly suitable if you are created some sort of root-view)
with RecursiveQuery
AS
(
SELECT a.ParentID theID, a.ParentID RootID
FROM [LessonCategory] AS a
UNION ALL
SELECT b.CategoryID, d.RootID
FROM [LessonCategory] AS b
INNER JOIN RecursiveQuery AS d
ON d.theID = b.ParentID
)
SELECT theID from RecursiveQuery where RootID = 3