MySQL查询页面祖先

Question

我有一个包含这些字段(id、parentID、name、content)的 MySQL 页面表.

页面层次结构是:

 - About Us 
   - History 
     - 2000
     - 2001

如果我在“2001”页面上，我如何创建一个查询来查找此页面的顶级祖先是“关于我们”？

Answer 1

一旦您重新设计表格以遵循 Nested Sets模型，查询将是

SELECT parent.name
FROM pages AS node,
pages  AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
AND node.name = '2001'
ORDER BY parent.lft
LIMIT 1

这会给你“关于我们”

如果您只允许特定级别的嵌套，您可以像该页面上显示的示例那样做一堆左连接:

SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4
FROM category AS t1
LEFT JOIN category AS t2 ON t2.parent = t1.category_id
LEFT JOIN category AS t3 ON t3.parent = t2.category_id
LEFT JOIN category AS t4 ON t4.parent = t3.category_id
WHERE t4.name = 'FLASH';

但是如果你想支持任意深度的嵌套，嵌套集是唯一的选择。花时间通读整页。它可能比您希望的更复杂，但一旦您了解它的工作原理，它就会非常强大。