在MySQL/PHP中实现嵌套集合排序

Question

我将尝试创建一个数据库，其中可以有n个类别及其子类别。

首先，我尝试创建这样的邻接模型数据库。

+-------------+----------------------+--------+
| category_id | name                 | parent |
+-------------+----------------------+--------+
|           1 | Electronics          |   NULL |
|           2 | Mobile               |      1 |
|           3 | Washing Machine      |      1 |
|           4 | Samsung              |      2 |
+-------------+----------------------+--------+

但是，当我删除一个节点时，我面临一个问题，例如如何管理已删除节点的子节点等。

然后，我尝试通过Joe Celko实现嵌套有序集。 每个图中的表结构：

Figure 1:
+----+-------------+-----+-----+
| id | name        | lft | rgt |
+----+-------------+-----+-----+
| 1  | Electronics | 1   | 2   |
+----+-------------+-----+-----+

Figure 2:
+----+-------------+-----+-----+
| id | name        | lft | rgt |
+----+-------------+-----+-----+
| 1  | Electronics | 1   | 4   |
+----+-------------+-----+-----+
| 2  | Mobile      | 2   | 3   |
+----+-------------+-----+-----+

Figure 3:
+----+-----------------+-----+-----+
| id | name            | lft | rgt |
+----+-----------------+-----+-----+
| 1  | Electronics     | 1   | 6   |
+----+-----------------+-----+-----+
| 2  | Mobile          | 2   | 3   |
+----+-----------------+-----+-----+
| 3  | Washing Machine | 4   | 5   |
+----+-----------------+-----+-----+

Figure 4:
+----+-----------------+-----+-----+
| id | name            | lft | rgt |
+----+-----------------+-----+-----+
| 1  | Electronics     | 1   | 8   |
+----+-----------------+-----+-----+
| 2  | Mobile          | 2   | 5   |
+----+-----------------+-----+-----+
| 3  | Washing Machine | 6   | 7   |
+----+-----------------+-----+-----+
| 4  | Samsung         | 3   | 4   |
+----+-----------------+-----+-----+

但我无法插入具有正确 rgt 和 lft 的新节点。我使用了这个，但它没有生成正确的 rgt 和 lft 值。

LOCK TABLE nested_category WRITE;

SELECT @myRight := rgt FROM nested_category
WHERE name = 'Mobile';

UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myRight;
UPDATE nested_category SET lft = lft + 2 WHERE lft > @myRight;

INSERT INTO nested_category(name, lft, rgt) VALUES('LG', @myRight + 1, @myRight + 2);

UNLOCK TABLES;

- jpm

---

你想如何管理子节点？它们会成为其祖父母的子节点，还是随其父节点一起被删除？ - Harsh Gupta

成为祖父母的孙子女。 - jpm

如果根节点被意外删除，应该发生什么？ - Harsh Gupta

所有子文件夹和它们的内容都将被删除。 - jpm

@jpm，你解决这个问题了吗？ - Blag

Answer 1

这个http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/是您的源代码吗？

您没有使用正确的查询，这个是“添加兄弟节点”的查询。

您需要的是“添加子节点”的查询：

LOCK TABLE nested_category WRITE;

SELECT @myLeft := lft FROM nested_category
WHERE name = 'Mobile';

UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myLeft;
UPDATE nested_category SET lft = lft + 2 WHERE lft > @myLeft;

INSERT INTO nested_category(name, lft, rgt) VALUES('LG', @myLeft + 1, @myLeft + 2);

UNLOCK TABLES;

- Blag

Answer 2

CREATE PROCEDURE nested_insert(_name VARCHAR(45))
BEGIN
DECLARE _number int;
set @var=0;

-- first insert paramater value(_name) into nested_table
INSERT into nested_table(name) VALUE(_name);

-- count the total row  value from nested table;
SELECT count(*) from  nested_table into _number;

-- first update the all lft column from top to button by varibale with increment
UPDATE nested_table set lft=(@var:=@var+1) where id <=_number;

-- second update the all rgt column from button to top by varibale with increment in descending order id
UPDATE nested_table set rgt=(@var:=@var+1) where id<=(_number+1)*2 ORDER BY id desc ;
end;

- Man