我正在阅读这篇文章,http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/.
我想举一个简单的例子,然后问你我如何得到想要的结果?下面是一个例子:
+---------+-----------------------------+
| product_id | product_name |
+---------+-----------------------------+
| 1 | Example Product |
+---------+-----------------------------+
+---------+-----------------------------+
| product_id | category_id |
+---------+-----------------------------+
| 1 | 2 |
| 1 | 4 |
+---------+-----------------------------+
+-------------+--------------------+------+------+
| category_id | name | lft | rgt |
+-------------+--------------------+------+------+
| 1 | Electronics | 1 | 8 |
| 2 | Televisions | 2 | 3 |
| 3 | Portable Electronics | 4 | 7 |
| 4 | CD Players | 5 | 6 |
+-------------+--------------------+------+------+
我希望在查询并在PHP中操作数据后,能够在HTML中显示以下结果:
"Example Product" Categories:
Electronics
Televisions
Portable Electronics
CD Players
你能帮助我完成PHP中的查询和操作以实现这个结果吗?
需要考虑的一些细节:
- 请注意这两个类别都在Electronics下,但"Electronics"在此处只出现一次,并在下面显示它所属的每个子类别
- 最终的结果应该是一个PHP多维数组,其中的类别包含一个子类别数组,每个子类别包含一个子类别数组(如果存在的话)
我认为打印深度对于在HTML中构建正确的树非常重要。
我觉得这是一个很好的挑战。。这是我的解决方案:
基本上:读取一个节点,然后rgt
小于rgt
的以下所有节点都是您的子节点,递归地执行此操作。我使用了peek
/consume
从mysql中读取,就像您通常使用的一样。
如果查询没有给出结果,或者数据集已损坏,则脚本将中断或循环。
class NestedNodeReader {
private $mysql_result;
private $peeked = false;
private $last_peek;
public function __construct($mysql_result) {
$this->mysql_result = $mysql_result;
}
public function getTree() {
$root = $this->consume();
$root["children"] = $this->getSubTree($root["rgt"]);
return $root;
}
private function getSubTree($stop_at) {
$nodes = array();
$node = $this->peek();
while ($node["rgt"] < $stop_at) {
$node = $this->consume();
$node["children"] = $this->getSubTree($node["rgt"]);
$nodes[] = $node;
$node = $this->peek();
if (false === $node) {
break;
}
}
return $nodes;
}
private function peek() {
if (false === $this->peeked) {
$this->peeked = true;
$this->last_peek = mysql_fetch_assoc($this->mysql_result);
}
return $this->last_peek;
}
private function consume() {
if (false === $this->peeked) {
return mysql_fetch_assoc($this->mysql_result);
} else {
$this->peeked = false;
return $this->last_peek;
}
}
}
$query = "SELECT node.name, node.lft, node.rgt
FROM nested_category AS node,
nested_category AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
AND parent.name = 'ELECTRONICS'
ORDER BY node.lft;"
$mysql_result = mysql_query($query);
$nnr = new NestedNodeReader($mysql_result);
print_r($nnr->getTree());