如何根据树遍历算法从此结果集生成树视图？

Question

我有这张桌子:

CREATE TABLE `categories` (
  `id` int(11) NOT NULL auto_increment,
  `category_id` int(11) default NULL,
  `root_id` int(11) default NULL,
  `name` varchar(100) collate utf8_unicode_ci NOT NULL,
  `lft` int(11) NOT NULL,
  `rht` int(11) NOT NULL,
  PRIMARY KEY  (`id`),
  KEY `category_id` (`category_id`),
  KEY `lft` (`lft`,`rht`),
  KEY `root_id` (`root_id`)
) 

基于这个问题: 将修改后的预订树遍历模型(嵌套集)转换为<ul>

不同的是,我在一张桌子上有很多树.每行都有一个代表其父级及其顶级父级的外键:category_id和root_id.我还有基于这个例子的lft和rht字段:http://articles.sitepoint.com/article/hierarchical-data-database/2

基于这些行:

INSERT INTO `categories` VALUES(1, NULL, NULL, 'Fruits', 1, 14);
INSERT INTO `categories` VALUES(2, 1, 1, 'Apple', 2, 3);
INSERT INTO `categories` VALUES(3, 1, 1, 'Orange', 4, 9);
INSERT INTO `categories` VALUES(4, 3, 1, 'Orange Type 1', 5, 6);
INSERT INTO `categories` VALUES(5, 3, 1, 'Orange Type 2', 7, 8);
INSERT INTO `categories` VALUES(6, 1, 1, 'Pear', 10, 11);
INSERT INTO `categories` VALUES(7, 1, 1, 'Banana', 12, 13);
INSERT INTO `categories` VALUES(8, NULL, NULL, 'Eletronics', 1, 14);
INSERT INTO `categories` VALUES(9, 8, 8, 'Cell Phones', 2, 3);
INSERT INTO `categories` VALUES(10, 8, 8, 'Computers', 4, 9);
INSERT INTO `categories` VALUES(11, 10, 8, 'PC', 5, 6);
INSERT INTO `categories` VALUES(12, 10, 8, 'MAC', 7, 8);
INSERT INTO `categories` VALUES(13, 8, 8, 'Printers', 10, 11);
INSERT INTO `categories` VALUES(14, 8, 8, 'Cameras', 12, 13);

如何构建表示此树的定序列表？

随着sql吼叫:

SELECT c. * , (COUNT( p.id ) -1) AS depth
FROM `categorias` AS p
CROSS JOIN categories AS c
WHERE (
c.lft
BETWEEN p.lft
AND p.rht
)
GROUP BY c.id
ORDER BY c.lft;

我得到了这个结果:

如您所见,我也需要通过root_id进行排序,以便生成正确的树.

另外,在获取树之后,有没有办法按名称命令每个节点？

Answer 1

我得到了它。

您需要做的就是将 root_id 也设置为顶级父级，以便您可以正确排序。

通过下面的查询，我可以拥有分离的树，并且仅更新我正在处理的树：

SELECT c . * , count( p.id ) AS depth
FROM `categories` c
CROSS JOIN categories p
WHERE (
c.lft
BETWEEN p.lft
AND p.rht
)
AND c.root_id = p.root_id
GROUP BY c.id
ORDER BY c.root_id, c.lft