Get all child categories from nested set AND join products table

Question

I want to retrieve all child categories with a given parent category AND I want to join my products table to that result. The result should be a breadcrumb navigation where a user could click on a parent category and retrieves all products in that category with the child categories.

Breadcrumb looks like that: Electronic >> Music >> MP3-Player >> Flash If a user clicks on "Music" the result should contain all products in the "Music" "MP3-Player" and "Flash" categories.

I use a nested set but I find it really difficult to handle it with complicated queries.

My database looks like that:

category_table: ID / Name / lft / rgt products_table: ID / Title / description / pic / category_id / ...

My query looks now like this:

    $result=mysql_query('SELECT *, node.id, node.name
FROM category AS node,
        category AS parent,
        category AS sub_parent,
        (
                SELECT node.name
                FROM category AS node,
                category AS parent
                WHERE node.lft BETWEEN parent.lft AND parent.rgt
                AND node.id = 23
                GROUP BY node.name
                ORDER BY node.lft
        )AS sub_tree JOIN products ON products.id = id
WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
        AND sub_parent.name = sub_tree.name
GROUP BY node.name
ORDER BY node.lft;') or die(mysql_error());

But this gives me the error "#1104 - The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET MAX_JOIN_SIZE=# if the SELECT is okay". I don't get it.

Answer 1

Try this PHP script. It may have a couple syntax errors in it, I haven't tested it yet, but it should do exactly what you want.

Its important to note, you need to add a field to your categories table, called category_parent_id and set its default value to either 0 or null .

class breadcrumbNav
{
    private $dataArray = array();
    private $breadcrumb = array();

    public function __construct()
    {
        $this->getAllRecords();
        return;
    }


    private function getAllRecords()
    {
        $result = $db->prepare("
            SELECT p.ID as product_id, p.title AS product_title, p.description AS product_description, p.pic AS product_picture, 
                   c.ID as category_id, c.Name as category_name, c.lft AS category_lft, c.rgt AS category_rgt, c.parent_id AS category_parent_id 
            FROM products p 
            LEFT JOIN categories c 
                 ON p.category_id = c.ID 
        ");

        $result->execute();

        $this->dataArray = $result->fetchAll(PDO::FETCH_ASSOC);
        return;
    }

    function buildBreadcrumb($recordId, $firstRun = true)
    {
         foreach($this->dataArray as $row)
         {
             if(($row['product_id']==$recordId && $firstRun) || ($row['category_id']==$recordId && $firstRun===false))
             {
                  $this->breadcrumb[] = '<a href="?categoryId=' . $row['category_id'] . '">' . $row['category_name'] . '</a>';

                  if($row['category_parent_id']!==0 && !is_null($row['category_parent_id']))
                  {
                      $this->buildBreadcrumb($this->buildBreadcrumb($row['category_parent_id'], false));
                  }
             }
         }

         return implode(' &gt;&gt; ', $this->breadcrumb;
    }
}



$currentProductId = 'ENTER THE PRODUCT ID HERE';
$breadcrumbObject = new breadcrumbNav();
$breadcrumb = $breadcrumbObject->buildBreadcrumb($currentProductId);