Mysql查询某个节点下的所有子节点

创建表

CREATE TABLE `dynamic_dict` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `company_id` int(11) NOT NULL,
  `dict_code` varchar(100) NOT NULL,
  `item_code` varchar(100) NOT NULL,
  `parent_item_code` varchar(100) DEFAULT NULL COMMENT '级联父级节点',
  `item_name` varchar(100) NOT NULL,
  `creater` varchar(45) NOT NULL,
  `create_time` datetime NOT NULL,
  `updater` varchar(45) NOT NULL,
  `update_time` datetime NOT NULL,
  `delete_flag` char(1) NOT NULL DEFAULT 'N',
  PRIMARY KEY (`id`),
  KEY `idx_dict_code` (`dict_code`)
) ENGINE=InnoDB AUTO_INCREMENT=216 DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;

创建数据

INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'yitian', '1', NULL, '父级节点', 'yitain', '2021-05-17 11:34:11', 'yitian', '2021-05-17 11:34:27', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'yitian', '2', '1', '子级节点', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'yitian', '3', '2', '三级节点', 'yitian', '2021-05-17 11:36:06', 'yitian', '2021-05-17 11:36:14', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'yitian', '4', '1', '二级节点', 'yitain', '2021-05-17 14:06:32', 'yitian', '2021-05-17 14:06:39', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'danxuan', '1', '', '单选1', 'yitain', '2021-06-03 19:16:25', 'yitian', '2021-06-03 19:16:29', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'danxuan', '2', '', '单选2', 'yitain', '2021-06-03 19:16:25', 'yitian', '2021-06-03 19:16:29', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian1', 'jilianitem', '1', '二级子节点1', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian1', 'jilianitem1', '1', '二级子节点2', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian1', 'jilianitem2', '2', '二级子节点3', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian1', 'jilianitem3', '2', '二级子节点4', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian2', 'jilianitemcode1', 'jilianitem', '三级子节点1', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian2', 'jilianitemcode2', 'jilianitem1', '三级子节点2', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian2', 'jilianitemcode3', 'jilianitem2', '三级子节点3', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');
INSERT INTO `dynamic_dict`( `company_id`, `dict_code`, `item_code`, `parent_item_code`, `item_name`, `creater`, `create_time`, `updater`, `update_time`, `delete_flag`) VALUES ( 7011, 'jilian2', 'jilianitemcode4', 'jilianitem3', '三级子节点4', 'yitian', '2021-05-17 11:35:10', 'yitian', '2021-05-17 11:35:17', 'N');

解析

-- 查询某个节点【@item_codes := '1'】下的所有子节点  
    -- 解析 
        -- 一、先赋值某个节点，获取所有节点得父节点是这个节点的子节点 FIND_IN_SET( parent_item_code, @item_codes )
        -- 二、赋值所有@item_codeds是最新的子节点的当前item_code @item_codeds := @item_codes【循环】
        -- 三、获取所有的节点 FIND_IN_SET( b.item_code, ID._item_codes )  结果排序

SELECT      
	ID.level, 
	b.item_code, 
	b.item_name AS itemName, 
	b.parent_item_code AS parentItemCode  
FROM 
	( 
	SELECT 
		@item_codeds := @item_codes AS _item_codes					
        --  三、查询所有parent_item_code在@item_codes中的数据
		(SELECT @item_codes := GROUP_CONCAT( item_code ) FROM	dynamic_dict  WHERE FIND_IN_SET( parent_item_code, @item_codes )) AS citem_codes, 
		@l := @l + 1 AS level  -- 二、设置当前等级
	FROM 
		dynamic_dict, 
		(SELECT @item_codes := '1', @l := 0) bb    --  一、开始 1、给item_codes 赋值节点数据  2、给@l赋值节点等级0
		WHERE @item_codes IS NOT NULL 
	) id, dynamic_dict b 
	WHERE 
	FIND_IN_SET( b.item_code, ID._item_codes ) 
	ORDER BY LEVEL,id