To clear $query object, to dump the query and nesting loop in Joomla

To clear the previous values from the query var.

/* This needs to be added while using nesting loop to clear the previous query in Joomla Component Writing. */
$query = $db->getQuery(true);

This is to print the built query or dump query.

/* This is to print the built query or dump query. */
echo $query->dump();

Find the sample query as below;

  $data = array();       
  $query->select('c.id, c.alias, c.title');
  $query->from('#__categories c');
  $query->where('c.alias not in ("admin") and c.extension="com_bmember" and published="1"');
  $query->order('c.title asc');
  $db->setQuery((string)$query);
  $categories = $db->loadObjectList();
  
  if (is_array($categories) && ($categories)>0)
  {
   $i=0;
   foreach ($categories as $category)
   {
    $data[$i]['catid'] = $category->id;
    $data[$i]['category'] = $category->title;
    $data[$i]['attributes'] = array();
    
    $query = $db->getQuery(true); // This needs to be added while using nesting loop to clear the previous query.
    $query->select('af.id, af.attribute, af.alias');
    $query->from('#__bmember_attribute_fields af');
    $query->where('af.catid="'.$category->id.'" and af.state="1"');
    $db->setQuery((string)$query);
    $rows = $db->loadObjectList();
    $query->order('af.attributes asc');
    $i++;
   }
  }