select Max and null value

[sql]

if my select statement have like
select ReceiveDate,InterviewDate, max(CompleteDate), max(ApprovalDate),
OfficerName,SecondOfficer, DATEDIFF( max(ApprovalDate), ReceiveDate) as diff from Pos as P, Status as A , Records as P2
where P.UserId=A.UserId and P.UserId=P2.userId
and ApprovalDate<>'Null'
and ReceiveDate>='2010-07-02' and ApprovalDate<='2010-09-02'
if not result on this range , I still get one row that contain Null value in the whole row?
Thank you
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