Question

sorry if you’ll find this question stupid, but I really need help. Here’s some info about it.

Database structure

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id | parent_id | level | name

1 | 0 | 1 | Home page

2 | 1 | 2 | Child of homepage

3 | 1 | 2 | Another child of homepage

4 | 2 | 3 | Sub child of page id 2

5 | 3 | 3 | Sub child of page id 3

---

Question

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How do I make the SQL statement to group my rows by level and make this output.

Desired output

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Home page

~~Child of homepage

~~~~Sub child of page id 2

~~Another child of homepage

~~~~Sub child of page id 3

I know how to do this with a recursion method, but I want to know if I can accomplish this with one SQL statement.

Answer 1

Well, you could order the data by parent_id so that it is sorted correctly:

$menu = mysql_query("SELECT * FROM menu ORDER BY parent_id, level, name");

Then, use the level to determine your indent:

while ($row = mysql_fetch_object($menu)) {
  echo str_repeat('~~', $row->level).' '.$row->name.'<br />';
}

Say you want them in nested lists or some other element (rather than indented by a prefix such as ‘~~’):

$level = 0;
echo '<ul>';
while ($row = mysql_fetch_object($menu)) {
  if ($row->level > $level) {
    echo '<ul>';
  } else if ($row->level < $level) {
    echo '</ul>';
  }
  echo '<li> '.$row->name.'</li>';
  $level = $row->level;
}
for ($i = $level; $i >= 0; $i--) {
  echo '</ul>';
}