Self Joins And Subquery

Hello,
I am in the process of debugging a fairly regular SQL statement. I want to simplify the SQL as much as possible for debugging. What I want to know is ... Is it reasonable to replace the return value of a sub query based on a self join. I thought this was legitimate, but it returns a different row count for each.

Here is what I am doing:


SELECT COUNT(DISTINCT(RELATIONSHIPNAME)) AS NUMRELS
--INTO boi.dbo.TBL_PERMGRADETEAMSUMMRELS
FROM CLIENT C, RELATIONSHIP R, PERMISSION P,REL_GRADEHISTORY G, REL_TEAMHISTORY T, TEAM A
WHERE C.RELATIONSHIPID=R.RELATIONSHIPID
AND G.RELATIONSHIPID=R.RELATIONSHIPID
AND C.CLIENTID=P.CLIENTID
AND T.TEAMID=A.TEAMID
AND R.RELATIONSHIPID=T.RELATIONSHIPID
AND A.REPORTINCLUDE = 'Y'
AND P.CHANGEDATE = (SELECT MAX(CHANGEDATE) FROM PERMISSION P1
WHERE P1.CLIENTID=C.CLIENTID
AND P1.CHANGEDATE <= '01/05/01'
AND P1.TYPE=P.TYPE)


I wanted to simplify the first subquery so I ran it independently and it recieved:

2000-11-17 00:00:00.000


Changed SQL:

SELECT COUNT(DISTINCT(RELATIONSHIPNAME)) AS NUMRELS
--INTO boi.dbo.TBL_PERMGRADETEAMSUMMRELS
FROM CLIENT C, RELATIONSHIP R, PERMISSION P,REL_GRADEHISTORY G, REL_TEAMHISTORY T, TEAM A
WHERE C.RELATIONSHIPID=R.RELATIONSHIPID
AND G.RELATIONSHIPID=R.RELATIONSHIPID
AND C.CLIENTID=P.CLIENTID
AND T.TEAMID=A.TEAMID
AND R.RELATIONSHIPID=T.RELATIONSHIPID
AND A.REPORTINCLUDE = 'Y'
AND P.CHANGEDATE = '17-11-2000'

I therefore put '17-11-2000' into the location of the first subquery ( A convert to varchar of the subquery result gave nov 17 2000).
The new query with the hardcoded date returns 9 rows, the older one returned 117.

Can anyone explain please?

Thanks

Lenin.