按级别分组行，并为每个行放置名称

Question

I have this table

id   ins  sec  div  subject  subjectHour  level
1     1    1    7   subName       5      level 1
2     1    2    7   subName2      4      level 1
3     1    2    7   subName3      4      level 2
4     1    1    7   subName4      6      level 2

I want to out put something like

level 1 subjects
subName
subName2

level 2 subjects
subName3
subName4

mysql JOIN the 4 tables

    $displayMat = $db->prepare('SELECT
     a.id, a.ins_id, a.sub_name, a.subHour, a.level,
     b.id, b.ins_name,
     c.id, sec_name,
     d.id, div_name
     FROM ins_subjects AS a
     INNER JOIN institutes AS b
     INNER JOIN ins_sections AS c
     INNER JOIN ins_division AS d
     WHERE a.ins_id=?
     GROUP BY a.id;
 ');

and here is the looping

$displayMat->bind_param('i', $inId);
  if ($displayMat->execute()) {
  $results = $displayMat->get_result();
  while ($m = mysqli_fetch_array($results)) {
<li>
  <div class="col-xs-3"><?php print $m['sub_name']; ?></div>
  <div class="col-xs-3"><?php print $m['ins_name']; ?></div>
  <div class="col-xs-3"><?php print $m['sec_name']; ?></div>
  <div class="col-xs-3"><?php print $m['div_name']; ?></div>
</li>
}

Answer 1

You SQL needs some join conditions, and the GROUP BY seem superfluous.

Starting with something like this:-

SELECT a.id, a.ins_id, a.sub_name, a.subHour, a.level,
        b.id, b.ins_name,
        c.id, sec_name,
        d.id, div_name
FROM ins_subjects AS a
INNER JOIN institutes AS b ON a.ins_id = b.id
INNER JOIN ins_sections AS c ON a.sec_id = c.id
INNER JOIN ins_division AS d ON a.div_id = d.id
ORDER BY a.level, a.sub_name

you can read each row in turn. Store the level and when the level changes from the previous row you output the level.

EDIT

Crudely done in php, something like this (not used lists here)

<?php
$displayMat->bind_param('i', $inId);
if ($displayMat->execute()) 
{
    $results = $displayMat->get_result();
    $prev_level = '';
    while ($m = mysqli_fetch_array($results)) 
    {
        if ($prev_level != $m['level'])
        {
            echo $m['level'];
        }
        $prev_level = $m['level'];
        ?>
          <div class="col-xs-3"><?php print $m['sub_name']; ?></div>
          <div class="col-xs-3"><?php print $m['ins_name']; ?></div>
          <div class="col-xs-3"><?php print $m['sec_name']; ?></div>
          <div class="col-xs-3"><?php print $m['div_name']; ?></div>
        <?php
    }
}