邻接表与嵌套集模型

我一直在寻找邻接列表和嵌套集模型,以找到最佳树的解决方案。

到目前为止,我认为嵌套集模型的主要优点之一是可以使用一个SQL查询和一些代码来获得完整的树。但是更新/插入节点比较复杂,整个树很容易被破坏。

然后我无意中发现了这两个帖子:

Recursive categories with a single query?

http://www.sitepoint.com/forums/showthread.php?t=570360

下面的代码允许我对一个SQL查询使用邻接列表。在我看来,邻接列表更容易更新,也不太可能损坏整个树。

你觉得这个密码怎么样?

生成多维数组以反映树结构

    $nodeList = array();
    $tree = array();

    $query = mysql_query("SELECT id, title, page_parent FROM categories ORDER BY page_parent");
    while($row = mysql_fetch_assoc($query)){
        $nodeList[$row['id']] = array_merge($row, array('children' => array()));
    }
    mysql_free_result($query);

    foreach($query AS $row){
        $nodeList[$row['id']] = array_merge($row, array('children' => array()));
    }

    foreach ($nodeList as $nodeId => &$node) {
        if (!$node['page_parent'] || !array_key_exists($node['page_parent'], $nodeList)) {
            $tree[] = &$node;
        } else {
            $nodeList[$node['page_parent']]['children'][] = &$node;
        }
    }

    unset($node);
    unset($nodeList);

使用嵌套节点准备无序列表

function printMenu ($arrTreeToTraverse, $ext = '.html', $breadcrumb = '') {

// Pre loop stuff
echo "<ul class=\"sf-menu\">\r\n";

foreach ($arrTreeToTraverse as $objItem) {

    // Stuff relevant to the item, before looping over its children
    if ($objItem['page_parent'] != 0) {
        $breadcrumb .= '/'.$objItem['uri'];
    }
    else
    {
        $breadcrumb .= $objItem['uri'];
    }

    if ($objItem['uri'] == 'index') {
        echo '<li><a href="/">'.$objItem['title'].'</a>';
    } else {
        echo '<li><a href="'$_SERVER['SERVER_NAME'].'/'.$breadcrumb.$ext.'">'.$objItem['title'].'</a>';
    }

    if ($objItem['children']) {
    echo "\r\n";

        // Call the function again on the children
        printMenu($objItem['children'], $ext, $breadcrumb);
    }// if

    // Extend breadcrumb if it is a child or
    // reset breadcrumb if first level of tree
    $parent = explode('/', $breadcrumb);
    if ($objItem['page_parent'] != 0) {
        $breadcrumb = $parent[0];
    } else {
        $breadcrumb = '';
    }

    echo "</li>\r\n";
}// foreach

// Post loop stuff
echo "</ul>\r\n";

}// function

printMenu($navigation, '.html');