通过内部联接从不同表中检索值

I am unable to retrieve values from different tables using inner join, The output always doesn't retrieve anything.. Also, there is no error message and I'm unable to determine what went wrong in my code.. Can someone please help? I would appreciate it very much. Here is a part of my code..

<?php
    $con=mysql_connect("localhost","root","");
    mysql_select_db("student_records",$con);
    if(isset($_COOKIE['username']))
    {
        if($_COOKIE['username']!='admin')
        {
            $tbl6=mysql_query("SELECT A.LName, A.FName, A.MName, B.YearLevel
            FROM student as A INNER JOIN stud_course as B ON A.StudNo=B.StudNo INNER JOIN course as C ON B.CourseCode=C.CourseCode INNER JOIN religion as D ON A.ReligionID=D.ReligionID
            WHERE A.StudNo = '".mysql_real_escape_string($_COOKIE['username'])."' ");
            while($row=mysql_fetch_array($tbl6))
            {
                echo "<td>".$row['LName']."</td><td>".$row['FName']."</td><td>".$row['MName']."</td><td>".$row['Course']."</td><td>".$row['YearLevel']."</td><td>".$row['EAdd']."</td><td>".$row['ReligionName']."</td></tr>";

            }
        }
    }
    ?>

Inner Joins require that data exist in both the tables included in the join. In your case, you have four tables, and any one of those tables could be missing relevant data:

SELECT A.LName, A.FName, A.MName, B.YearLevel, C.Course
FROM student as A 
INNER JOIN stud_course as B ON 
    A.StudNo=B.StudNo 
INNER JOIN course as C ON 
    B.CourseCode=C.CourseCode 
INNER JOIN religion as D ON A.ReligionID=D.ReligionID
WHERE A.StudNo = '".mysql_real_escape_string($_COOKIE['username'])."' "

• If there is no record in the student table with a StudNo equal to the username cookie, you will get no data.
• If the student does not have any records in the stud_course table, you will get no data.
• If the CourseCode in stud_course does not exist in the course table, you will get no data.
• If the student's ReligionID is null or has a religion that is not in the religion table, you will get no data.

I would suggest breaking the SQL into smaller pieces (or possibly switching each INNER JOIN to LEFT OUTER JOIN) to debug and discover where the problem is.

Note, you have to make sure to add the Course and Eadd (not sure what table that's from) fields to your select list if you are going to try to use it.