Question

I am writing a php site using a mysql database for a class of mine and cannot for the life of me figure out what is wrong with it. I have a query that works locally on my machine (on an identical db to the one on the teacher’s server) but when I upload it, it doesn’t work. The problem is that the query is returning 0 results even though the db has info in it that should be showing.

function bigAssQuery($whereCondition)
{

    $queries[] = 'CREATE TEMPORARY TABLE subAssignments (SELECT ua.assignmentid, ua.assignmentnum, ua.description
                    FROM Course c JOIN UserAssignment ua ON ua.crn = c.CRN AND ua.term = c.term
                    WHERE c.CRN = "'.$_SESSION["crnum"].'" AND c.term = "'.$_SESSION["mysem"].'")';

    $queries[] = 'CREATE TEMPORARY TABLE subStudents (SELECT s.studentid, s.lastname, s.firstname
                    FROM Course c JOIN Student s ON s.crn = c.CRN AND s.term = c.term
                    WHERE c.CRN = "'.$_SESSION["crnum"].'" AND c.term = "'.$_SESSION["mysem"].'")';

    $queries[] = 'CREATE TEMPORARY TABLE subRubric(SELECT assignmentid, re.rubricelementid, re.learning_goal_char
                    FROM RubricElement re JOIN RubricAssignmentRelation rar ON re.rubricelementid = rar.rubricelementid)';

    $queries[] = 'CREATE TEMPORARY TABLE subAssignRub(SELECT subAssignments.assignmentid, rubricelementid, learning_goal_char, assignmentnum, description
                    FROM subRubric JOIN subAssignments ON subAssignments.assignmentid = subRubric.assignmentid)';

    $queries[] = 'CREATE TEMPORARY TABLE subAssignRubStud (SELECT *
                    FROM subAssignRub CROSS JOIN subStudents)';

    $queries[] = 'CREATE TEMPORARY TABLE subAssignInstRubStud (SELECT sars.assignmentid, ai.ainstanceid, rubricelementid, learning_goal_char, assignmentnum, description, sars.studentid, lastname, firstname
                    FROM subAssignRubStud sars LEFT JOIN AssignmentInstance ai ON sars.studentid = ai.studentid AND sars.assignmentid = ai.assignmentid)';

    $queries[] = 'CREATE TEMPORARY TABLE subTotal (SELECT assignmentid, siars.ainstanceid, s.ainstanceid As scoreAID, siars.rubricelementid, learning_goal_char, assignmentnum, description, studentid, lastname, firstname, score
                    FROM subAssignInstRubStud siars LEFT JOIN Score s ON siars.ainstanceid = s.ainstanceid AND siars.rubricelementid = s.rubricelementid
                    ORDER BY lastname, assignmentid)';

    $queries[] = 'SELECT *
        FROM subTotal
        '.$whereCondition.' Order By lastname, assignmentnum, learning_goal_char';  

    return($queries);
}

Then when the db is queried the code looks like this. . .

$queries = bigAssQuery($whereCondition);


$result = 1;
foreach($queries as $query)
{
    $result = $db->query($query);

    if(!$result)
    {
        echo '<script type="text/javascript"> 
                window.onload=function(){ alert("Error: Could not extract course information. Please try again later."); } 
             </script> ';
        exit;
    }
}

$num_rows = $result->num_rows;

I assure you that the local and remote databases are identical. I see no reason why no results are coming back. I did test a few simple temp tables to see if the server wasn’t reading those tables for some reason, but they weren’t an issue in my tests. I would try with nested subqueries, but it gets so convoluted so quickly that I can’t organize it. Maybe there is a better way?
Also, just to clarify the queries aren’t failing, they just aren’t returning anything when I know that they should.
I apologize for the wall of text, but any help is appreciated.

EDIT: I really don’t know which of the queries the problem lies. I do know that I’m probably missing some important information. Part of that lies in my web inexperience. I test locally first because I’ve got the debugger working, but I honestly don’t know how to do remote debugging. I’m using netbeans and xdebug. If someone could suggest a how to get remote debugging set up I would probably be able to come up with some better data. Any suggestions would be helpful

EDIT AGAIN: Found the problem. Embarrassingly enough it was an error in data entry; one of my foreign keys was incorrectly entered. Thanks everybody for pointing me in the right direction.

Answer 1

On having a quick look, your code is stoping the execution of the PHP inappropriately. You should at least the let the remainder to continue. Simply exit out of loop using break; instead.

if(!$result)
{
    echo '<script type="text/javascript"> 
            window.onload=function(){ alert("Error: Could not extract course information. Please try again later."); } 
         </script> ';
    break; //exit the loop only NOT THE PHP's Execution
}

Furthermore, check every query individually and run them separately on phpMyAdmin to see, if they are executing correctly. Find the break point and fix the error.