好吧,让我们做一些赏金狩猎;)
步骤 0 - 清理示例:
如前所述,您的示例数据已损坏,因为它未定义有效的嵌套集。如果从应用获取此数据,则应检查插入/删除逻辑。
因此,为了进行测试,我使用了一个经过消毒的版本,如下所示:
(MySQL在这里,因为它是手头的第一个)
CREATE TABLE t_categories`(
`id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
`title` VARCHAR(45) NOT NULL,
`lft` INTEGER UNSIGNED NOT NULL,
`rght` INTEGER UNSIGNED NOT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 1',1,16);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 2',2,3);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 3',4,7);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 4',5,6);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 5',8,13);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 6',9,12);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 7',10,11);
INSERT INTO t_categories (title, lft, rght) VALUES ('Cat 8',14,15);
步骤1 - 让数据库对嵌套集进行排序
,其中主要是作为在数据库中存储树的便捷方式而发明的,因为它们使得查询子树,父关系以及在这种情况下特别有趣的是顺序和深度变得非常容易:
SELECT node.title, (COUNT(parent.title) - 1) AS depth
FROM t_categories AS node
CROSS JOIN t_categories AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rght
GROUP BY node.title
ORDER BY node.lft
这将按整齐顺序返回您的集合,从根节点开始,一直持续到预序的末尾。最重要的是,它将每个节点的深度添加为正整数,指示节点在根(级别 0)以下的级别数。对于上面的示例数据,结果将为:
title, depth
'Cat 1', 0
'Cat 2', 1
'Cat 3', 1
'Cat 4', 2
'Cat 5', 1
'Cat 6', 2
'Cat 7', 3
'Cat 8', 1
在代码中:
// Grab ordered data
$query = '';
$query .= 'SELECT node.title, (COUNT(parent.title) - 1) AS depth';
$query .= ' FROM t_categories AS node';
$query .= ' CROSS JOIN t_categories AS parent';
$query .= ' WHERE node.lft BETWEEN parent.lft AND parent.rght';
$query .= ' GROUP BY node.title';
$query .= ' ORDER BY node.lft';
$result = mysql_query($query);
// Build array
$tree = array();
while ($row = mysql_fetch_assoc($result)) {
$tree[] = $row;
}
生成的数组将如下所示:
Array
(
[0] => Array
(
[title] => Cat 1
[depth] => 0
)
[1] => Array
(
[title] => Cat 2
[depth] => 1
)
...
)
步骤 2 - 输出为 HTML 列表片段:
使用 while 循环:
// bootstrap loop
$result = '';
$currDepth = -1; // -1 to get the outer <ul>
while (!empty($tree)) {
$currNode = array_shift($tree);
// Level down?
if ($currNode['depth'] > $currDepth) {
// Yes, open <ul>
$result .= '<ul>';
}
// Level up?
if ($currNode['depth'] < $currDepth) {
// Yes, close n open <ul>
$result .= str_repeat('</ul>', $currDepth - $currNode['depth']);
}
// Always add node
$result .= '<li>' . $currNode['title'] . '</li>';
// Adjust current depth
$currDepth = $currNode['depth'];
// Are we finished?
if (empty($tree)) {
// Yes, close n open <ul>
$result .= str_repeat('</ul>', $currDepth + 1);
}
}
print $result;
与递归函数相同的逻辑:
function renderTree($tree, $currDepth = -1) {
$currNode = array_shift($tree);
$result = '';
// Going down?
if ($currNode['depth'] > $currDepth) {
// Yes, prepend <ul>
$result .= '<ul>';
}
// Going up?
if ($currNode['depth'] < $currDepth) {
// Yes, close n open <ul>
$result .= str_repeat('</ul>', $currDepth - $currNode['depth']);
}
// Always add the node
$result .= '<li>' . $currNode['title'] . '</li>';
// Anything left?
if (!empty($tree)) {
// Yes, recurse
$result .= renderTree($tree, $currNode['depth']);
}
else {
// No, close remaining <ul>
$result .= str_repeat('</ul>', $currNode['depth'] + 1);
}
return $result;
}
print renderTree($tree);
两者都将输出以下结构:
<ul>
<li>Cat 1</li>
<li>
<ul>
<li>Cat 2</li>
<li>Cat 3</li>
<li>
<ul>
<li>Cat 4</li>
</ul>
</li>
<li>Cat 5</li>
<li>
<ul>
<li>Cat 6</li>
<li>
<ul>
<li>Cat 7</li>
</ul>
</li>
</ul>
</li>
<li>Cat 8</li>
</ul>
</li>
</ul>
Nitpickers corner:提问者明确要求,但有序无序列表!?加油。。。<ul>
;-)