我想将目录(存在于磁盘上)存储到数据库中,同时保持它们的层次结构/树结构。
这是一个数字:
(ROOT) / \ Dir2 Dir3 / \ \ Dir4 Dir5 Dir6 / Dir7
我正在使用 SQLite 数据库。
请给我建议:
将上述结构存储在 SQLite 数据库中的 SQL 查询,以及
当我选择一个目录时检索目录完整路径的查询。
即假设我选择
Dir7
那么我应该得到像ROOT/Dir2/Dir4/Dir7
这样的完整路径
最佳答案
这是 SQLite 的快速关闭表示例。我没有包含将项目插入现有树的语句。相反,我只是手动创建了语句。您可以在 Models for hierarchical data 中找到插入和删除语句。幻灯片。
为了在插入目录 ID 时保持理智,我重命名了目录以匹配它们的 ID:
(ROOT)
/ \
Dir2 Dir3
/ \ \
Dir4 Dir5 Dir6
/
Dir7
创建表
CREATE TABLE `filesystem` (
`id` INTEGER,
`dirname` TEXT,
PRIMARY KEY (`id`)
);
CREATE TABLE `tree_path` (
`ancestor` INTEGER,
`descendant` INTEGER,
PRIMARY KEY (`ancestor`, `descendant`)
);
将目录插入文件系统
表
INSERT INTO filesystem (id, dirname) VALUES (1, 'ROOT');
INSERT INTO filesystem (id, dirname) VALUES (2, 'Dir2');
INSERT INTO filesystem (id, dirname) VALUES (3, 'Dir3');
INSERT INTO filesystem (id, dirname) VALUES (4, 'Dir4');
INSERT INTO filesystem (id, dirname) VALUES (5, 'Dir5');
INSERT INTO filesystem (id, dirname) VALUES (6, 'Dir6');
INSERT INTO filesystem (id, dirname) VALUES (7, 'Dir7');
创建闭包表路径
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 1);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 2);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 3);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 4);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 5);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 6);
INSERT INTO tree_path (ancestor, descendant) VALUES (1, 7);
INSERT INTO tree_path (ancestor, descendant) VALUES (2, 2);
INSERT INTO tree_path (ancestor, descendant) VALUES (2, 4);
INSERT INTO tree_path (ancestor, descendant) VALUES (2, 5);
INSERT INTO tree_path (ancestor, descendant) VALUES (2, 7);
INSERT INTO tree_path (ancestor, descendant) VALUES (3, 3);
INSERT INTO tree_path (ancestor, descendant) VALUES (3, 6);
INSERT INTO tree_path (ancestor, descendant) VALUES (4, 4);
INSERT INTO tree_path (ancestor, descendant) VALUES (4, 7);
INSERT INTO tree_path (ancestor, descendant) VALUES (5, 5);
INSERT INTO tree_path (ancestor, descendant) VALUES (6, 6);
INSERT INTO tree_path (ancestor, descendant) VALUES (7, 7);
运行一些查询
# (ROOT) and subdirectories
SELECT f.id, f.dirname FROM filesystem f
JOIN tree_path t
ON t.descendant = f.id
WHERE t.ancestor = 1;
+----+---------+
| id | dirname |
+----+---------+
| 1 | ROOT |
| 2 | Dir2 |
| 3 | Dir3 |
| 4 | Dir4 |
| 5 | Dir5 |
| 6 | Dir6 |
| 7 | Dir7 |
+----+---------+
# Dir3 and subdirectories
SELECT f.id, f.dirname
FROM filesystem f
JOIN tree_path t
ON t.descendant = f.id
WHERE t.ancestor = 3;
+----+---------+
| id | dirname |
+----+---------+
| 3 | Dir3 |
| 6 | Dir6 |
+----+---------+
# Dir5 and parent directories
SELECT f.id, f.dirname
FROM filesystem f
JOIN tree_path t
ON t.ancestor = f.id
WHERE t.descendant = 5;
+----+---------+
| id | dirname |
+----+---------+
| 1 | ROOT |
| 2 | Dir2 |
| 5 | Dir5 |
+----+---------+
# Dir7 and parent directories
SELECT f.id, f.dirname
FROM filesystem f
JOIN tree_path t
ON t.ancestor = f.id
WHERE t.descendant = 7;
+----+---------+
| id | dirname |
+----+---------+
| 1 | ROOT |
| 2 | Dir2 |
| 4 | Dir4 |
| 7 | Dir7 |
+----+---------+
SELECT f.id, f.dirname
FROM filesystem f
JOIN tree_path t
ON t.ancestor = f.id
WHERE t.descendant = (
SELECT id
FROM filesystem
WHERE dirname LIKE '%7%'
);
+----+---------+
| id | dirname |
+----+---------+
| 1 | ROOT |
| 2 | Dir2 |
| 4 | Dir4 |
| 7 | Dir7 |
+----+---------+
关于sql - 文件系统中目录路径的分层/树数据库,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6802539/