从嵌套的set和join products表中获取所有子类别

Question

我希望检索具有给定父类别的所有子类别，并希望将我的products表连接到该结果。结果应该是一个面包屑导航，用户可以在其中单击父类别，并检索该类别中的所有产品以及子类别。

Breadcrumb看起来是这样的：Electronic >> Music >> MP3-Player >> Flash如果用户点击“音乐”，结果应该包含“音乐”、“mp3播放器”和"Flash“类别中的所有产品。

我使用嵌套set，但我发现很难处理复杂的查询。

我的数据库是这样的：

图片: ID /名称/ lft / rgt products_table: ID /标题/描述/图片/ category_id / ...

我的查询现在看起来像这样：

    $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());

但这给出了错误"#1104 - SELECT将检查多于MAX_JOIN_SIZE的行；如果SELECT没有问题，请检查WHERE并使用SET SQL_BIG_SELECTS=1或SET MAX_JOIN_SIZE=#“。我还是不明白。

Answer 1

试试这个PHP脚本。它可能有几个语法错误，我还没有测试它，但它应该可以做你想要的。

需要注意的是，您需要向categories表中添加一个名为category_parent_id的字段，并将其缺省值设置为0或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);