我花了最后几个小时尝试在线查找此问题的解决方案。我已经找到了很多有关如何从嵌套集转换为邻接集的示例，但是很少有相反的例子。我发现的示例不起作用或不使用MySQL过程。不幸的是，我无法使用此项目的过程。我需要一个纯PHP解决方案。
我有一个使用下面的邻接模型的表:
id parent_id category
1 0 Books
2 0 CD's
3 0 Magazines
4 1 Books/Hardcover
5 1 Books/Large Format
6 3 Magazines/Vintage
我想将其转换为下面的嵌套集表:
id left right category
0 1 14 Root Node
1 2 7 Books
4 3 4 Books/Hardcover
5 5 6 Books/Large Format
2 8 9 CD's
3 10 13 Magazines
6 11 12 Magazines/Vintage
这是我需要的图像:
我有一个功能，该功能基于来自本论坛帖子(http://www.sitepoint.com/forums/showthread.php?t=320444)的伪代码，但是它不起作用。我得到多行具有相同的左值。这不应该发生。
<?php
/**
--
-- Table structure for table `adjacent_table`
--
CREATE TABLE IF NOT EXISTS `adjacent_table` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`father_id` int(11) DEFAULT NULL,
`category` varchar(128) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=8 ;
--
-- Dumping data for table `adjacent_table`
--
INSERT INTO `adjacent_table` (`id`, `father_id`, `category`) VALUES
(1, 0, 'ROOT'),
(2, 1, 'Books'),
(3, 1, 'CD''s'),
(4, 1, 'Magazines'),
(5, 2, 'Hard Cover'),
(6, 2, 'Large Format'),
(7, 4, 'Vintage');
--
-- Table structure for table `nested_table`
--
CREATE TABLE IF NOT EXISTS `nested_table` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`lft` int(11) DEFAULT NULL,
`rgt` int(11) DEFAULT NULL,
`category` varchar(128) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
*/
mysql_connect('localhost','USER','PASSWORD') or die(mysql_error());
mysql_select_db('DATABASE') or die(mysql_error());
adjacent_to_nested(0);
/**
* adjacent_to_nested
*
* Reads a "adjacent model" table and converts it to a "Nested Set" table.
* @param integer $i_id Should be the id of the "root node" in the adjacent table;
* @param integer $i_left Should only be used on recursive calls. Holds the current value for lft
*/
function adjacent_to_nested($i_id, $i_left = 0)
{
// the right value of this node is the left value + 1
$i_right = $i_left + 1;
// get all children of this node
$a_children = get_source_children($i_id);
foreach ($a_children as $a)
{
// recursive execution of this function for each child of this node
// $i_right is the current right value, which is incremented by the
// import_from_dc_link_category method
$i_right = adjacent_to_nested($a['id'], $i_right);
// insert stuff into the our new "Nested Sets" table
$s_query = "
INSERT INTO `nested_table` (`id`, `lft`, `rgt`, `category`)
VALUES(
NULL,
'".$i_left."',
'".$i_right."',
'".mysql_real_escape_string($a['category'])."'
)
";
if (!mysql_query($s_query))
{
echo "<pre>$s_query</pre>\n";
throw new Exception(mysql_error());
}
echo "<p>$s_query</p>\n";
// get the newly created row id
$i_new_nested_id = mysql_insert_id();
}
return $i_right + 1;
}
/**
* get_source_children
*
* Examines the "adjacent" table and finds all the immediate children of a node
* @param integer $i_id The unique id for a node in the adjacent_table table
* @return array Returns an array of results or an empty array if no results.
*/
function get_source_children($i_id)
{
$a_return = array();
$s_query = "SELECT * FROM `adjacent_table` WHERE `father_id` = '".$i_id."'";
if (!$i_result = mysql_query($s_query))
{
echo "<pre>$s_query</pre>\n";
throw new Exception(mysql_error());
}
if (mysql_num_rows($i_result) > 0)
{
while($a = mysql_fetch_assoc($i_result))
{
$a_return[] = $a;
}
}
return $a_return;
}
?>
这是上面脚本的输出。
如您所见，有多个行共享lft值“1”，与“2”相同。在嵌套集中，left和right的值必须唯一。这是一个如何为嵌套集中的左ID和右ID手动编号的示例:
图片来源:Gijs Van Tulder，ref article
最佳答案
我在网上找到了答案，并在此页面上更新了问题，以向其他人展示它是如何完成的。
更新-解决了问题
首先，我错误地认为需要更改源表(相邻列表格式的源表)以包含源节点。不是这种情况。其次，我通过BING found a class达到了目的。我已将其更改为PHP5，并将原始作者的mysql相关位转换为基本PHP。他正在使用一些数据库类(class)。如果需要，可以稍后将它们转换为自己的数据库抽象类。
显然，如果“源表”中还有其他要移到嵌套集表的列，则必须在下面的类中调整write方法。
希望这将在将来使其他人摆脱同样的问题。
<?php
/**
--
-- Table structure for table `adjacent_table`
--
DROP TABLE IF EXISTS `adjacent_table`;
CREATE TABLE IF NOT EXISTS `adjacent_table` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`father_id` int(11) DEFAULT NULL,
`category` varchar(128) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=8 ;
--
-- Dumping data for table `adjacent_table`
--
INSERT INTO `adjacent_table` (`id`, `father_id`, `category`) VALUES
(1, 0, 'Books'),
(2, 0, 'CD''s'),
(3, 0, 'Magazines'),
(4, 1, 'Hard Cover'),
(5, 1, 'Large Format'),
(6, 3, 'Vintage');
--
-- Table structure for table `nested_table`
--
DROP TABLE IF EXISTS `nested_table`;
CREATE TABLE IF NOT EXISTS `nested_table` (
`lft` int(11) NOT NULL DEFAULT '0',
`rgt` int(11) DEFAULT NULL,
`id` int(11) DEFAULT NULL,
`category` varchar(128) DEFAULT NULL,
PRIMARY KEY (`lft`),
UNIQUE KEY `id` (`id`),
UNIQUE KEY `rgt` (`rgt`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
*/
/**
* @class tree_transformer
* @author Paul Houle, Matthew Toledo
* @created 2008-11-04
* @url http://gen5.info/q/2008/11/04/nested-sets-php-verb-objects-and-noun-objects/
*/
class tree_transformer
{
private $i_count;
private $a_link;
public function __construct($a_link)
{
if(!is_array($a_link)) throw new Exception("First parameter should be an array. Instead, it was type '".gettype($a_link)."'");
$this->i_count = 1;
$this->a_link= $a_link;
}
public function traverse($i_id)
{
$i_lft = $this->i_count;
$this->i_count++;
$a_kid = $this->get_children($i_id);
if ($a_kid)
{
foreach($a_kid as $a_child)
{
$this->traverse($a_child);
}
}
$i_rgt=$this->i_count;
$this->i_count++;
$this->write($i_lft,$i_rgt,$i_id);
}
private function get_children($i_id)
{
return $this->a_link[$i_id];
}
private function write($i_lft,$i_rgt,$i_id)
{
// fetch the source column
$s_query = "SELECT * FROM `adjacent_table` WHERE `id` = '".$i_id."'";
if (!$i_result = mysql_query($s_query))
{
echo "<pre>$s_query</pre>\n";
throw new Exception(mysql_error());
}
$a_source = array();
if (mysql_num_rows($i_result))
{
$a_source = mysql_fetch_assoc($i_result);
}
// root node? label it unless already labeled in source table
if (1 == $i_lft && empty($a_source['category']))
{
$a_source['category'] = 'ROOT';
}
// insert into the new nested tree table
// use mysql_real_escape_string because one value "CD's" has a single '
$s_query = "
INSERT INTO `nested_table`
(`id`,`lft`,`rgt`,`category`)
VALUES (
'".$i_id."',
'".$i_lft."',
'".$i_rgt."',
'".mysql_real_escape_string($a_source['category'])."'
)
";
if (!$i_result = mysql_query($s_query))
{
echo "<pre>$s_query</pre>\n";
throw new Exception(mysql_error());
}
else
{
// success: provide feedback
echo "<p>$s_query</p>\n";
}
}
}
mysql_connect('localhost','USER','PASSWORD') or die(mysql_error());
mysql_select_db('DATABASE') or die(mysql_error());
// build a complete copy of the adjacency table in ram
$s_query = "SELECT `id`,`father_id` FROM `adjacent_table`";
$i_result = mysql_query($s_query);
$a_rows = array();
while ($a_rows[] = mysql_fetch_assoc($i_result));
$a_link = array();
foreach($a_rows as $a_row)
{
$i_father_id = $a_row['father_id'];
$i_child_id = $a_row['id'];
if (!array_key_exists($i_father_id,$a_link))
{
$a_link[$i_father_id]=array();
}
$a_link[$i_father_id][]=$i_child_id;
}
$o_tree_transformer = new tree_transformer($a_link);
$o_tree_transformer->traverse(0);
?>
这是输出: