Function to Return the Amount of Children in a Tree

/*
<Purpose>Returns the no of children given node id</Purpose> 
 <Input><Param>node id</Param> </Input>
<Output> <Value>No Of Children</Value></Output>
 <Author Email = "damcalcan@hotmai.com">Calin Damian</Author> 
 </Documentation>*/CREATE FUNCTION ufs_GetNoOfChildren (@parentId int )
RETURNS int AS
BEGIN

DECLARE  @noOfChildren int 

SELECT @noOfChildren = COUNT (*)
FROM dbo.staff C
WHERE  C.supervisor = @parentId

--call the function recursively
SELECT @noOfChildren = @noOfChildren + dbo.ufs_GetNoOfChildrenV1 (employee)
FROM dbo.staff C
WHERE  C.supervisor = @parentId

RETURN @noOfChildren
END


--- how the function is called 
SELECT dbo.ufs_GetNoOfChildren(1)