MySQL 的嵌套类别

Question

API 像这样返回类别：

[1] => Array
        (
            [category_id] => 14308
            [parent_id] => 14308
            [level] => 0
        )

    [2] => Array
        (
            [category_id] => 179836
            [parent_id] => 14308
            [level] => 1
        )

        [3] => Array
            (
                [category_id] => 230022
                [parent_id] => 179836
                [level] => 2
            )

我需要像这样将它们插入数据库中：

╔═════════════╦═══════════╗
║ category_id ║ parent_id ║
╠═════════════╬═══════════╣
║       14308 ║         0 ║
║      179836 ║     14308 ║
║      230022 ║    179836 ║
╚═════════════╩═══════════╝

...这很容易，但category_to_path 表很棘手，我似乎无法弄清楚。它需要是这样的：

╔═════════════╦═════════╦═══════╗
║ category_id ║ path_id ║ level ║
╠═════════════╬═════════╬═══════╣
║       14308 ║   14308 ║     0 ║
║      179836 ║   14308 ║     0 ║
║      179836 ║  179836 ║     1 ║
║      230022 ║   14308 ║     0 ║
║      230022 ║  179836 ║     1 ║
║      230022 ║  230022 ║     2 ║
╚═════════════╩═════════╩═══════╝

这是我目前所拥有的：

$path_ids;
for ($i=0; $i <= ($category->CategoryLevel-1); $i++) { 
// -1 cause the API returns a non zero-based level

  $path_ids[$i]['category_id'] = $category->CategoryID;

  if ($category->CategoryLevel-1 == $i) {
    $path_ids[$i]['path_id'] = $category->CategoryParentID[0];
  }
  elseif ($category->CategoryLevel-1) {
    // ?
  }

  $path_ids[$i]['level'] = $i;

}

Answer 1

我会在从 API 获取数组后尝试重写数组，使其看起来像这样：

[14308] => Array
(
    [parent_id] => 14308
    [level] => 0
)

[179836] => Array
(
    [parent_id] => 14308
    [level] => 1
)

[230022] => Array
(
    [parent_id] => 179836
    [level] => 2
)

当您从 API 获取数组时，您可以使用简单的 foreach 循环对其进行处理。

$arrayFromApi = apiCallToObtainData();    
$newArray = [];
foreach($arrayFromApi as $value){
    $newArray[$value['category_id']] = [
        $value['parent_id'], 
        $value=['level'],
    ];
}

现在您可以轻松访问父母，因此实现您所需要的应该不难。

Answer 2

以下查询应为您提供类别和路径。它没有给出级别，因为您的原始数据缺少任何类型的行号。如果您想获得关卡，您可能需要使用一些动态 SQL。

我使用的策略是交叉连接类别，从而生成所有可能的起点和终点。它还会生成一些表不支持的路径。为了删除这些不需要的路径，我会根据子查询检查每个路径，以确保可以通过在 3 步或更短的时间内从类别遍历到路径来创建它。

SELECT t1.category_id AS category_id,
       t2.category_id AS path_id
FROM yourTable t1
CROSS JOIN yourTable t2
INNER JOIN
(
    SELECT t1.category_id AS category_id_1,
           t2.category_id AS category_id_2,
           t3.category_id AS category_id_3
    FROM yourTable t1
    LEFT JOIN yourTable t2
        ON t1.parent_id = t2.category_id
    LEFT JOIN yourTable t3
        ON t2.parent_id = t3.category_id
) t2
    ON t1.category_id = t2.category_id_1 AND
       t2.category_id IN (t2.category_id_1, t2.category_id_2, t2.category_id_3)
ORDER BY category_id,
         path_id