有没有简单的方法来查询节点的子级？

Question

最近，我一直在使用嵌套集模型中的废话。我喜欢为几乎所有有用的操作和视图设计查询。我坚持的一件事是如何选择节点的直接子代（并且 仅
选择子代，而不是进一步的子代！）。

老实说，我确实知道一种方法-但它涉及大量的SQL。我敢肯定有一个更直接的解决方案。

Answer 1

您是否阅读过您张贴的文章？在“查找节点的直接下属”标题下

SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM nested_category AS node,
    nested_category AS parent,
    nested_category AS sub_parent,
    (
        SELECT node.name, (COUNT(parent.name) - 1) AS depth
        FROM nested_category AS node,
        nested_category AS parent
        WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.name = 'PORTABLE ELECTRONICS'
        GROUP BY node.name
        ORDER BY node.lft
    )AS sub_tree
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
HAVING depth <= 1
ORDER BY node.lft;

但是，我要做的（这是作弊）是将嵌套集与邻接列表结合在一起-我在表中嵌入了一个“ parent_id”，因此我可以轻松地请求一个节点的子代。