存储嵌套标签的最佳数据模型？

Question

我正在尝试为电子商务网站制作面包屑。像这样的东西：

Home > Kitchen > Serving and reception > Spoon 

每一项都是一个标签。因此，

tags

表是基于父级/历史的。这是表结构的示例：

// tags
+----+-----------------------+-----------+
| id |         name          | parent_id |
+----+-----------------------+-----------+
| 1  | Home                  | Null      |
| 2  | Kitchen               | 1         |
| 3  | Serving and reception | 2         |
| 4  | Spoon                 | 3         |
| 5  | Digital               | NULL      |
| 6  | Communication         | 5         |
| 7  | Cellphone             | 6         |
| .. | ...                   | ...       |
+----+-----------------------+-----------+

在这种情况下，很难以正确的顺序获取所有嵌套相关项。我应该改变数据库结构吗？我的意思是，拥有这样一个数据模型的最佳方法是什么？

---

注意到，目前我使用 PHP 循环来获取相关标签并制作面包屑。另外，我使用 MySQL 版本

8.0.37

。

Answer 1

您可以像这样使用递归 CTE：

WITH RECURSIVE TagHierarchy AS (
    SELECT id, name, parent_id name AS path
    FROM tags
    WHERE parent_id IS NULL

    UNION ALL

    SELET t.id, t.name, t.parent_id,
          CONCAT(th.path, ' > ', t.name) AS path
    FROM tags t
    JOIN TagHierarchy th ON t.parent_id = th.id
)
SELECT id, name, path
FROM TagHierarchy
ORDER BY path;

结果

+----+-----------------------+----------------------------------+
| id | name                  | path                             |
+----+-----------------------+----------------------------------+
|  1 | Home                  | Home                             |
|  2 | Kitchen               | Home > Kitchen                   |
|  3 | Serving and reception | Home > Kitchen > Serving and reception |
|  4 | Spoon                 | Home > Kitchen > Serving and reception > Spoon |
|  5 | Digital               | Digital                          |
|  6 | Communication         | Digital > Communication          |
|  7 | Cellphone             | Digital > Communication > Cellphone |
+----+-----------------------+----------------------------------+