Displaying null value to gridview from database

Question

Hello everyone, I once again would like your assistance. I have this query below:

SELECT  DISTINCT sg.StudentID,
                     (sm.Fname + ' ' + sm.Lname + ' - ' + sm.NickName) AS StudentName,

                     ISNULL(sg.Q1, 0) as Q1,
                     ISNULL(sg.Q2, 0) as Q2

    FROM    dbo.tblStudentGradesTwoTerms sg INNER JOIN
        dbo.tblEnrollmentHeader eh ON sg.EnrollmentID = eh.EnrollmentID INNER JOIN
        dbo.tblStudentTeacherMaster sm ON sg.StudentID = sm.StudentTeacherID AND    eh.StudentID = sm.StudentTeacherID

    WHERE   sg.SchoolCode = @SchoolCode AND
            sg.SchoolYear = @SchoolYear AND
            sg.GradeLvl = @GradeLvl AND
            sg.SubjectID = @SubjectCode

and this is what it displays in my gridview:

 

 

How not to display the 0? I want to display only blank if students doesn't have grades yet.

Thanks for any assistance.