在 while 中显示来自 SQL 的单独结果

Question

Hello i'm a beginner in these matters.

Yesterday i got acquainted with something like a group_concat() function of sql. I've got tables called "subjects" and "grades". In subjects there is stored "id, name, subject_type" and in grades is "id, grade, subject_type".

So if subjects got subject_type = 1 it will shows all of grades for that type.

I've created code like this:

<?php 
$sqltest1 = "SELECT s.id AS id,  s.name AS name, group_concat(g.grade SEPARATOR ',') as grades, s.teacher_1 as teacher_1
FROM subjects s 
INNER JOIN grades g ON (g.subject_type = s.subject_type)
GROUP BY s.id"; 
?>
<table class="table table-bordered">
      <thead>
        <tr>
          <th class="col-1">#</th>
          <th class="col-3 text-center">Subject</th>
          <th class="col-6 text-center">Grade</th>
          <th class="col-1 text-center">Options</th>
        </tr>
      </thead>
      <tbody>
    <!-- ###################################################################### -->
      <?php
      $result = $conn->query($sqltest1);
      if ($result->num_rows > 0) {
        $i = 1;

        // output data of each row
        while($row = $result->fetch_assoc()) {
          //$id = $row['id'];
          echo "<tr>";
          echo "<td scope='row'>". $i ."</td>";
          echo "<td>". $row['name'] ."</td>";
          echo "<td><span class='bg-primary'>". $row["grades"] ."</span></td>";
          echo "<td class='text-center'>". $row['teacher_1']."</td>";
          echo "</tr>";
          $i++;
      }
 
    
    } else {
    echo "";
    }
    
    ?>
    
    <!-- ###################################################################### -->
    </tbody>
    </table>

So my problem is that i can't retrive separate grades in one column. I would like to get all grades of a given type but to shows as separate grade.

Answer 1

The while should be like this (check the apart inside the while) You get an array by splitting the value by every char you use to separate it: a comma. Then you foreach all the elements and write a span inside.

    // output data of each row
    while($row = $result->fetch_assoc()) {
      //$id = $row['id'];
      echo "<tr>";
      echo "<td scope='row'>". $i ."</td>";
      echo "<td>". $row['name'] ."</td>"; 

      echo "<td>";
      $arrayGrades = explode(",",  $row["grades"]);
      foreach ($arrayGrades as $grade) {
      echo "<span class='bg-primary'>". $grade ."</span>";
      }
      echo "</td>";
      
      echo "<td class='text-center'>". $row['teacher_1']."</td>";
      echo "</tr>";
      $i++;
  }