如何在没有子类别的情况下检索子类别?

以下是我的声明:

SELECT (
  COUNT( parent.categoryName ) - ( sub_tree.depth +1 ) ) AS depth,
  CONCAT( REPEAT( '', ( COUNT( parent.categoryName ) - ( sub_tree.depth +1 ) ) ) , node.categoryName ) AS categoryName

FROM 
  Categories AS node,
  Categories AS parent,
  Categories AS sub_parent,
 (
  SELECT node.categoryName, (
     COUNT( parent.categoryName ) -1) AS depth
     FROM 
       Categories AS node,
       Categories AS parent
     WHERE 
       node.categoryLft BETWEEN parent.categoryLft AND parent.categoryRgt
   AND node.categoryName LIKE 'Product'

     GROUP BY node.categoryName
     ORDER BY node.categoryLft
  ) AS sub_tree
WHERE 
    node.categoryLft BETWEEN parent.categoryLft AND parent.categoryRgt
AND node.categoryLft BETWEEN sub_parent.categoryLft AND sub_parent.categoryRgt
AND sub_parent.categoryName = sub_tree.categoryName

GROUP BY node.categoryName
ORDER BY node.categoryLft

它工作得很好,但我希望修改它,只获得选定类别(此处为“产品”)旁边的第一个节点,而不包含子类别的子节点

比如:

• A型

  • 亚型

• B型

我想要“A型”,“B型”。

顺便说一下,这是我的桌子:

CREATE TABLE `Categories` (
 `categoryId` int(11) NOT NULL auto_increment,
 `categoryLft` int(11) NOT NULL,
 `categoryRgt` int(11) NOT NULL,
 `categoryName` varchar(255) default NULL,
 `categoryAlias` varchar(255) default NULL,
 PRIMARY KEY  (`categoryId`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8