详细聊一聊mysql的树形结构存储以及查询详细聊一聊mysql的树形结构存储

序
存储parent
存储path
MPTT(Modified Preorder Tree Traversal)
小结
doc

序本文主要研究一下mysql的树形结构存储及查询

存储parent

这种方式就是每个节点存储自己的parent_id信息

建表及数据准备

CREATE TABLE `menu` (`id` int(11) NOT NULL AUTO_INCREMENT,`name` varchar(50) NOT NULL,`parent_id` int(11) NOT NULL DEFAULT '0',PRIMARY KEY (`id`)) ENGINE=InnoDB; INSERT INTO `menu` (`id`, `name`, `parent_id`) VALUES(1, 'level1a',0),(2, 'level1b', 0),(3, 'level2a-1a',1),(4, 'level2b-1a',1),(5, 'level2a-1b', 2),(6, 'level2b-1b', 2),(7, 'level3-2a1a', 3),(8, 'level3-2b1a', 4),(9, 'level3-2a1b', 5),(10, 'level3-2b1b', 6);

查询

-- 查询跟节点下的所有节点SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3FROM menu AS t1LEFT JOIN menu AS t2 ON t2.parent_id = t1.idLEFT JOIN menu AS t3 ON t3.parent_id = t2.idWHERE t1.name = 'level1a'; +---------+------------+-------------+| lev1| lev2| lev3|+---------+------------+-------------+| level1a | level2a-1a | level3-2a1a || level1a | level2b-1a | level3-2b1a |+---------+------------+-------------+-- 查询叶子节点SELECT t1.name FROMmenu AS t1 LEFT JOIN menu as t2ON t1.id = t2.parent_idWHERE t2.id IS NULL; +-------------+| name|+-------------+| level3-2a1a || level3-2b1a || level3-2a1b || level3-2b1b |+-------------+

存储及修改上比较方便，就是要在sql里头查询树比较费劲，一般是加载到内存由应用自己构造

存储path

这种方式在存储parent的基础上，额外存储path，即从根节点到该节点的路径

建表及数据准备

CREATE TABLE `menu_path` (`id` int(11) NOT NULL AUTO_INCREMENT,`name` varchar(50) NOT NULL,`parent_id` int(11) NOT NULL DEFAULT '0',`path` varchar(255) NOT NULL DEFAULT '',PRIMARY KEY (`id`)) ENGINE=InnoDB; INSERT INTO `menu_path` (`id`, `name`, `parent_id`, `path`) VALUES(1, 'level1a', 0, '1/'),(2, 'level1b', 0, '2/'),(3, 'level2a-1a',1, '1/3'),(4, 'level2b-1a',1, '1/4'),(5, 'level2a-1b', 2, '2/5'),(6, 'level2b-1b', 2, '2/6'),(7, 'level3-2a1a', 3, '1/3/7'),(8, 'level3-2b1a', 4, '1/4/8'),(9, 'level3-2a1b', 5, '2/5/9'),(10, 'level3-2b1b', 6, '2/6/10');

查询

-- 查询某个节点的所有子节点select * from menu_path where path like '1/%'+----+-------------+-----------+-------+| id | name| parent_id | path|+----+-------------+-----------+-------+| 1| level1a| 0| 1/|| 3| level2a-1a| 1| 1/3|| 4| level2b-1a| 1| 1/4|| 7| level3-2a1a | 3| 1/3/7 || 8| level3-2b1a | 4| 1/4/8 |+----+-------------+-----------+-------+

查找某个节点及其子节点比较方面，就是修改比较费劲，特别是节点移动，所有子节点的path都得跟着修改

MPTT(Modified Preorder Tree Traversal)

文章图片

【详细聊一聊mysql的树形结构存储以及查询】不存储parent_id，改为存储lft,rgt，它们的值由树的先序遍历顺序决定

建表及数据准备

CREATE TABLE `menu_preorder` (`id` int(11) NOT NULL,`name` varchar(50) NOT NULL,`lft` int(11) NOT NULL DEFAULT '0',`rgt` int(11) NOT NULL DEFAULT '0',PRIMARY KEY (`id`)) ENGINE=InnoDB; 1(level1a)142(level2a)78(level2b)133(level3a-2a)4 5(level3b-2a)6 9(level3c-2b)10 11(level3d-2b)12INSERT INTO `menu_preorder` (`id`, `name`, `lft`, `rgt`) VALUES(1, 'level1a', 1, 14),(2, 'level2a',2, 7),(3, 'level2b',8, 13),(4, 'level3a-2a', 3, 4),(5, 'level3b-2a', 5, 6),(6, 'level3c-2b', 9, 10),(7, 'level3d-2b', 11, 12); select * from menu_preorder+----+------------+-----+-----+| id | name| lft | rgt |+----+------------+-----+-----+| 1| level1a| 1| 14|| 2| level2a| 2| 7|| 3| level2b| 8| 13|| 4| level3a-2a | 3| 4|| 5| level3b-2a | 5| 6|| 6| level3c-2b | 9| 10|| 7| level3d-2b | 11| 12|+----+------------+-----+-----+

查询

-- 查询某个节点及其子节点，比如level2bselect * from menu_preorder where lft between 8 and 13+----+------------+-----+-----+| id | name| lft | rgt |+----+------------+-----+-----+| 3| level2b| 8| 13|| 6| level3c-2b | 9| 10|| 7| level3d-2b | 11| 12|+----+------------+-----+-----+-- 查询所有叶子节点SELECT nameFROM menu_preorderWHERE rgt = lft + 1; +------------+| name|+------------+| level3a-2a || level3b-2a || level3c-2b || level3d-2b |+------------+-- 查询某个节点及其父节点SELECT parent.*FROM menu_preorder AS node,menu_preorder AS parentWHERE node.lft BETWEEN parent.lft AND parent.rgtAND node.name = 'level2b'ORDER BY parent.lft; +----+---------+-----+-----+| id | name| lft | rgt |+----+---------+-----+-----+| 1| level1a | 1| 14|| 3| level2b | 8| 13|+----+---------+-----+-----+-- 树形结构展示SELECT CONCAT( REPEAT(' ', COUNT(parent.name) - 1), node.name) AS nameFROM menu_preorder AS node,menu_preorder AS parentWHERE node.lft BETWEEN parent.lft AND parent.rgtGROUP BY node.nameORDER BY node.lft; +--------------+| name|+--------------+| level1a||level2a||level3a-2a ||level3b-2a ||level2b||level3c-2b ||level3d-2b |+--------------+