-- Data (corrected column names):

if object_id('tempdb..#Position') is not null drop table #Position;

create table #Position
(
PosId Int,
ReportTo Int,
EmpId Int,
IsVacant Int,
LevelNo Int
);
insert into #Position values (1, 0, 123, 0, 0);
insert into #Position values (2, 1, 124, 0, 1);
insert into #Position values (3, 1, 125, 0, 1);
insert into #Position values (4, 2, 126, 0, 2);
insert into #Position values (5, 2, Null, 1, 2);
insert into #Position values (6, 2, 128, 0, 2);
insert into #Position values (7, 5, 129, 0, 3);
insert into #Position values (8, 5, 130, 0, 3);

select * from #Position;

-- Query:

;WITH PCCET AS 
(
SELECT RootID = PosId, 
	PosId, EmpId
FROM #Position 
UNION ALL
SELECT cte.RootID, d.PosId, d.EmpId
FROM PCCET cte
INNER JOIN #Position d ON d.ReportTo = cte.PosId
)
--select * from PCCET order by rootid
select P.PosId, 
	ISNULL(cnt.Children, 0) as PCnt
from #Position P 
LEFT OUTER JOIN (
	SELECT posid = RootID, Children = COUNT(*)
	FROM PCCET
	WHERE EmpId is not null
	AND RootId <> PosId
	GROUP BY RootID
) cnt ON cnt.posid = p.PosId