从MySQL中的菜单表获得一致的菜单树数据
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13-09-2019 - |
题
我有一棵树/祖先/查询问题我解决不了:
我有一个表保持菜单数据和包含该菜单的所有祖先的表:
table menu table ancestors
+-----+------------+--------+ +---------+--------------+-------+
| id | title | active | | menu_id | ancestor_id | level |
+-----+------------+--------+ +---------+--------------+-------+
| 1 | Home | 0 | | 1 | 0 | 0 |
| 2 | News | 0 | | 2 | 1 | 1 |
| 3 | Foo | 0 | | 3 | 2 | 2 |
| 4 | Bar | 1 | | 3 | 1 | 1 |
| 5 | Downloads | 1 | | 4 | 3 | 3 |
+-----+------------+--------+ | 4 | 2 | 2 |
| 4 | 1 | 1 |
| 5 | 1 | 1 |
+---------+--------------+-------+
我与他们的祖先所有的活动菜单项容易搭配:
SELECT menu.id, menu.title, GROUP_CONCAT(ancestors.ancestor_id) as ancestors
FROM menu, ancestors
WHERE menu.active = 1
GROUP BY (menu.id);
+----+-----------+----------+
| id | title |ancestors |
+----+-----------+----------+
| 4 | Bar | 3,2,1 |
| 5 | Downloads | 1 |
+----+-----------+----------+
但我怎么能得到所有的对树必要的祖先吗?在我的结果我需要进入Foo和新闻,让我获得了洽树。它应该是这样的:
+----+-----------+----------+
| id | title |ancestors |
+----+-----------+----------+
| 2 | News | 1 |
| 3 | Foo | 2,1 |
| 4 | Bar | 3,2,1 |
| 5 | Downloads | 1 |
+----+-----------+----------+
如何具有查询以怎样?
解决方案
当我做到这一点,我结构ancestors
表略有不同。相反level
的,我存储pathlength
。还可以存储一个行每个菜单项为指向自身,为0的路径长度。
+---------+--------------+------------+
| menu_id | ancestor_id | pathlength |
+---------+--------------+------------+
| 1 | 1 | 0 |
| 2 | 2 | 0 |
| 3 | 3 | 0 |
| 4 | 4 | 0 |
| 5 | 5 | 0 |
| 2 | 1 | 1 |
| 3 | 2 | 2 |
| 3 | 1 | 1 |
| 4 | 3 | 3 |
| 4 | 2 | 2 |
| 4 | 1 | 1 |
| 5 | 1 | 1 |
+---------+--------------+------------+
这些“反身性”条目允许您加入集中的活动菜单项,关闭表。更改级别的光程可以让你从一组祖先排除自反项。
现在,你可以查询中的“活动”菜单项,包括活动的菜单项本身的祖先所有菜单项:
SELECT a2.menu_id, m2.title, GROUP_CONCAT(a2.ancestor_id) AS ancestors
FROM menu m1
JOIN ancestors a1 ON (m1.id = a1.menu_id)
JOIN ancestors a2 ON (a1.ancestor_id = a2.menu_id AND a2.pathlength > 0)
JOIN menu m2 ON (a2.menu_id = m2.id)
WHERE m1.active = 1
GROUP BY a2.menu_id;
结果:
+---------+-----------+-----------+
| menu_id | title | ancestors |
+---------+-----------+-----------+
| 2 | News | 1 |
| 3 | Foo | 2,1 |
| 4 | Bar | 3,2,1 |
| 5 | Downloads | 1 |
+---------+-----------+-----------+
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