查询结果在PHP / HTML显示中显示不需要的SQL SUM公式文本

Question

I have a table 'marks' with fields Q1mark, Q2mark, Q3mark . . . Q50mark corresponding to the 50 questions in an exam.

I want to display how many marks each question attracted, and I'd like to order the questions by difficulty.

So I loop through 50 and put the key=>value pairs in a HTML table:

for ($i=1; $i<=50; $i++)
 {

        $stmt = $db->prepare("SELECT (SUM(Q".$i."mark)) FROM marks");
        $stmt->execute();
        $results = $stmt->fetchAll(PDO::FETCH_ASSOC);

      foreach ($results as $result) 
          { 
            echo '<tr>';
            foreach ($result as $key=>$value)
                  { 
                echo '<td>'; echo $key; echo '</td>';
                echo '<td>'; echo $value; echo '</td>';

              } 
        echo '</tr>';
              }   
    }

What I get is:

------------------------
| (SUM(Q1mark)) |   18 |
| (SUM(Q2mark)) |   20 |
| (SUM(Q3mark)) |   8  |
| (SUM(Q4mark)) |   12 |
------------------------

but what I want is:

----------------
| Q3mark |  8  |
| Q4mark |  12 |
| Q1mark |  18 |
| Q2mark |  20 |
----------------

How do I get rid of the displayed formula text?, And order the data by difficulty?

Answer 1

One way to do this is to store all the result in a 2d array.

$final_result = array();
for ($i=1; $i<=50; $i++)
 {

        $stmt = $db->prepare("SELECT (SUM(Q".$i."mark)) FROM marks");
        $stmt->execute();
        $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
       $final_result[] = $results;

 }
sort($final_result);
for($i=0;$i<count($final_result);$i++){
    echo $final_result[$i][“Q”.$i.”mark”];
}

Have a look at sorting arrays in PHP https://www.w3schools.com/php/php_arrays_sort.asp

Answer 2

I'll close this question with an answer to the question posed in the question title that was supplied in a comment, otherwise it'll appear unanswered.

To get of the SUM formula text I need to SELECT the result AS . . . and use the variable $i in the column name:

(SUM(Q".$i."mark)) AS Q$i

I'll open a new question with a tighter focus on the other problem I mentioned, namely ordering the query results.