Category Hierarchy （PHP/MySQL）

php mysql categories hierarchy

2022-08-30 22:42:23

我正在尝试从层次结构中的MySQL数据库获取所有类别和子类别：

我的结果应该是这样的（只是例子）：

第 A 类

子类 1

Sub_Sub_Cat 1

Sub_Sub_Cat 2

Sub_Cat 2

类别 B

第 C 类

...

我的SQL代码：

CREATE TABLE IF NOT EXISTS `categories` (
   `category_id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
   `parent_id` mediumint(8) unsigned NOT NULL DEFAULT '0' COMMENT 'for sub-categories'
  PRIMARY KEY (`category_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 ;

简单地说，如何使用PHP代码在hirarchy中获取它？

答案 1

使用邻接列表模型时，可以在一次传递中生成结构。

摘自 One Pass 父子数组结构（2007 年 9 月;作者：Nate Weiner）：：

$refs = array();
$list = array();

$sql = "SELECT item_id, parent_id, name FROM items ORDER BY name";

/** @var $pdo \PDO */
$result = $pdo->query($sql);

foreach ($result as $row)
{
    $ref = & $refs[$row['item_id']];

    $ref['parent_id'] = $row['parent_id'];
    $ref['name']      = $row['name'];

    if ($row['parent_id'] == 0)
    {
        $list[$row['item_id']] = & $ref;
    }
    else
    {
        $refs[$row['parent_id']]['children'][$row['item_id']] = & $ref;
    }
}

在链接的文章中，下面是一个用于创建输出列表的代码段。它是递归的，如果一个节点有一个子节点，它会再次调用自己来构建子树。

function toUL(array $array)
{
    $html = '<ul>' . PHP_EOL;

    foreach ($array as $value)
    {
        $html .= '<li>' . $value['name'];
        if (!empty($value['children']))
        {
            $html .= toUL($value['children']);
        }
        $html .= '</li>' . PHP_EOL;
    }

    $html .= '</ul>' . PHP_EOL;

    return $html;
}

相关问题：

如何从对象的数组记录集中获取嵌套的HTML列表？

答案 2

我有一个新想法，我认为这将是很好的。其思路是这样的：在category_parent列中，我们将插入对此节点的所有父节点的引用。

+----+----------------------+-----------------+
| id | category_name        |    hierarchy    |
+----+----------------------+-----------------+
| 1  | cat1                 |        1        |
+----+----------------------+-----------------+
| 2  | cat2                 |        2        |
+----+----------------------+-----------------+
| 3  | cat3                 |        3        |
+----+----------------------+-----------------+
| 4  | subcat1_1            |       1-4       |
+----+----------------------+-----------------+
| 5  | subcat1_2            |       1-5       |
+----+----------------------+-----------------+
| 6  | subsubcat1_1         |      1-4-6      |
+----+----------------------+-----------------+
| 7  | subsubcat1_2         |      1-4-7      |
+----+----------------------+-----------------+
| 8  | subsubcat1_3         |      1-4-8      |
+----+----------------------+-----------------+
| 9  | subsubcat1_3_1       |     1-4-8-9     |
+----+----------------------+-----------------+
| 10 | subsubcat1_3_2       |     1-4-8-10    |
+----+----------------------+-----------------+
| 11 | subsubcat1_3_1_1     |    1-4-8-9-11   |
+----+----------------------+-----------------+
| 12 | subsubsubcat1_3_1_1  |   1-4-8-9-12    |
+----+----------------------+-----------------+
| 13 | subsubsubcat1_3_1_2  |  1-4-8-9-11-13  |
+----+----------------------+-----------------+
| 14 | subsubsubcat1_2_1_3  |  1-4-8-9-11-14  |
+----+----------------------+-----------------+

如果你看一下我更新的表格，你会注意到每条记录都有一个链接到它的父级，不仅是直接的，还有所有父级。对于这项工作，我做了一些修改，插入到：

Insert into table_name (category_name, hierarchy) values ('new_name', (concat(parent_hierarch, '-', (SELECT Auto_increment FROM information_schema.tables WHERE table_name='table_name'))))

现在，让我们进行所需的查询：

1-汽车的所有子类别：

select * from table_name where hierarchy like '1-%'

2-如果您需要BLACK的所有父级，您只需键入：

select * from table_name where hierarchy = '1-4-8-9' or hierarchy = '1-4-8' or hierarchy = '1-4' or hierarchy = '1'

（您可以从php构建该查询，在'-'char处拆分层次结构字段）

3-查看所有类别，包括级别和直接父级：

select *, SUBSTR(hierarchy, 1, (LENGTH(hierarchy) - LENGTH(id) - 1)) as parent, LENGTH(hierarchy) - LENGTH(REPLACE(hierarchy, '-', '')) as level From table_name

+----+----------------------+-----------------+-----------+--------+
| id | category name        |    hierarchy    |   parent  |  level |
+----+----------------------+-----------------+-----------+--------+
| 1  | cat1                 |        1        |           |    0   |
+----+----------------------+-----------------+-----------+--------+
| 2  | cat2                 |        2        |           |    0   |
+----+----------------------+-----------------+-----------+--------+
| 3  | cat3                 |        3        |           |    0   |
+----+----------------------+-----------------+-----------+--------+
| 4  | subcat1_1            |       1-4       |     1     |    1   |
+----+----------------------+-----------------+-----------+--------+
| 5  | subcat1_2            |       1-5       |     1     |    1   |
+----+----------------------+-----------------+-----------+--------+
| 6  | subsubcat1_1         |      1-4-6      |    1-4    |    2   |
+----+----------------------+-----------------+-----------+--------+
| 7  | subsubcat1_2         |      1-4-7      |    1-4    |    2   |
+----+----------------------+-----------------+-----------+--------+
| 8  | subsubcat1_3         |      1-4-8      |    1-4    |    2   |
+----+----------------------+-----------------+-----------+--------+
| 9  | subsubcat1_3_1       |     1-4-8-9     |   1-4-8   |    3   |
+----+----------------------+-----------------+-----------+--------+
| 10 | subsubcat1_3_2       |     1-4-8-10    |   1-4-8   |    3   |
+----+----------------------+-----------------+-----------+--------+
| 11 | subsubcat1_3_1_1     |    1-4-8-9-11   |  1-4-8-9  |    4   |
+----+----------------------+-----------------+-----------+--------+
| 12 | subsubsubcat1_3_1_1  |   1-4-8-9-12    |  1-4-8-9  |    4   |
+----+----------------------+-----------------+-----------+--------+
| 13 | subsubsubcat1_3_1_2  |  1-4-8-9-11-13  |1-4-8-9-11 |    5   |
+----+----------------------+-----------------+-----------+--------+
| 14 | subsubsubcat1_2_1_3  |  1-4-8-9-11-14  |1-4-8-9-11 |    5   |
+----+----------------------+-----------------+-----------+--------+

这是一个新想法，需要一些改进。