协调具有动态行和列的表的问题

Question

Bear with me here--this may be a bit confusing.

I am retrieving two sets of data with SQL. Here's the code, with the query. I'm using Zend Framework.

$assignments = $db->fetchAll("SELECT id,name,class FROM assignments");
foreach($assignments as $a) {
    $assignmentID = $a['id'];
    $studentData = $db->fetchAll(
        "SELECT student,assignment,status,assignmentID FROM student_assignments WHERE assignmentID='$assignmentID'"
    );

    echo "<th>".$a['name']."</th>";

    foreach($studentData as $s) {
        $bottom .= "<tr><td>" . $s['student'] . " " . $s['assignmentID'] 
                   . " ".$s['status'] . "</td></tr>";
        $i++;
    }
}
echo "</tr>$bottom;";

Here's what the output looks like in the HTML:

|Assignment on 07/07/2012|  |Assignment on 07/12/2012|   |Assignment on 07/15/2012|
117 1 Y
332 1 N
36 1 N
420 1 N
332 1 Y
326 2 N
212 2 N
461 2 N
117 2 N
212 2 N
212 3 N
326 3 N
117 3 Y
420 3 Y

Now the top part is working great -- it's dynamically showing each assignment in the database. But I've been trying to figure out a way to get the appropriate data to show under those columns, to no effect. This is the closest I've gotten to making it look somewhat correct.

Essentially, the data that has "2" and "3" in the middle should go into the 2nd and 3rd columns, respectively. But this isn't happening because all the data is stored into the $bottom variable, rather than the data for each assignment.

Does anyone have any suggestions? This is driving me crazy, and I feel like the solution is staring me in the face.

Thanks!

Answer 1

First you want to iterate through every of your student assignments, and left join the assignments table to it so you can know the name of the assignment that it is related to.

$students = $db->fetchAll('SELECT sa.student,sa.assignment,sa.status,sa.assignmentID,a.name
                           FROM student_assignments AS sa
                           LEFT JOIN assignments AS a ON sa.assignmentID=a.id');

Then with the results, you can build an array to regroup everyone with the same assignment:

$columns = Array();
foreach($students as $s) {
    $row = '<tr><td>'.$s['student'].' '.$s['assignmentID'].' '.$s['status'].'</td></tr>';
    array_push($columns[$s['name']], $row);
}

Then with this array, you can finally print your content:

foreach ($columns as $key=>$value) {
    echo '<th>'.$key.'</th>';
    foreach ($value as $v) {
        echo $v;
    }
}

Of course this can be more compact (reduced into nested loops), and I have no way to fully test it, but it should help you in your process ;)