我正在使用树存储。封闭表模式。
https://towardsdatascience.com/closure-table-pattern-to-model-hierarchies-in-nosql-c1be6a87e05b
如何获得没有孙子和曾孙的子节点？
我有一个 sql 查询：
SELECT p.id, p.name, count(*) - l.level AS level
FROM tree_Path t,
( SELECT count(*) -1 AS level
FROM tree_path
WHERE children = 3
) l,
( SELECT *
FROM category_name f
INNER JOIN tree_Path t
ON f.id = t.children
WHERE t.parent = 3
AND t.children!=t.parent
) p
WHERE p.children = t.children
GROUP BY p.id, p.name, l.level;
它返回一棵完整的后代树，包括孙子和曾孙。
+----+----------------------------+-------+
| id | name | level |
+----+----------------------------+-------+
| 7 | Audio & Video Accessories | 2 |
| 8 | Camera & Photo Accessories | 2 |
| 15 | 3D Glasses | 3 |
| 16 | Antennas | 3 |
| 17 | Accessory Bundles | 3 |
| 18 | Bags & Cases | 3 |
+----+----------------------------+-------+
我需要归还没有孙子和曾孙的孩子。
+----+----------------------------+-------+
| id | name | level |
+----+----------------------------+-------+
| 7 | Audio & Video Accessories | 2 |
| 8 | Camera & Photo Accessories | 2 |
+----+----------------------------+-------+
怎么做？
数据库测试
-- phpMyAdmin SQL Dump
-- version 5.1.0
-- https://www.phpmyadmin.net/
--
-- Host: localhost
-- Generation Time: Aug 02, 2021 at 01:15 PM
-- Server version: 8.0.25
-- PHP Version: 8.0.3
SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
START TRANSACTION;
SET time_zone = "+00:00";
/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8mb4 */;
--
-- Database: `closure_table`
--
-- --------------------------------------------------------
--
-- Table structure for table `category_name`
--
CREATE TABLE `category_name` (
`id` bigint NOT NULL,
`name` varchar(255) COLLATE utf8mb4_ru_0900_ai_ci DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_ru_0900_ai_ci;
--
-- Dumping data for table `category_name`
--
INSERT INTO `category_name` (`id`, `name`) VALUES
(1, 'Electronics'),
(2, 'Computers'),
(3, 'Accessories & Supplies'),
(4, 'Camera & Photo'),
(5, 'Computer accessories and peripherals'),
(6, 'Computer components'),
(7, 'Audio & Video Accessories'),
(8, 'Camera & Photo Accessories'),
(9, 'Accessories'),
(10, 'Bags & Cases'),
(11, 'Audio & Video Accessories'),
(12, 'Blank Media'),
(13, 'Computer screws'),
(14, 'Table Barebones'),
(15, '3D Glasses'),
(16, 'Antennas'),
(17, 'Accessory Bundles'),
(18, 'Bags & Cases'),
(19, 'Accessory Kits'),
(20, 'Bags & Cases'),
(21, 'Bag & Case Accessories'),
(22, 'Binocular Cases'),
(23, 'Computer headsets'),
(24, 'Computer microphones'),
(25, 'Discs BD-R'),
(26, 'Discs BD-RE'),
(27, 'bolts'),
(28, 'frame'),
(29, 'lamps'),
(30, 'coasters');
-- --------------------------------------------------------
--
-- Table structure for table `tree_path`
--
CREATE TABLE `tree_path` (
`children` bigint NOT NULL,
`parent` bigint NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_ru_0900_ai_ci;
--
-- Dumping data for table `tree_path`
--
INSERT INTO `tree_path` (`children`, `parent`) VALUES
(1, 1),
(3, 1),
(4, 1),
(7, 1),
(8, 1),
(9, 1),
(10, 1),
(15, 1),
(16, 1),
(17, 1),
(18, 1),
(19, 1),
(20, 1),
(21, 1),
(22, 1),
(2, 2),
(5, 2),
(6, 2),
(11, 2),
(12, 2),
(13, 2),
(14, 2),
(23, 2),
(24, 2),
(25, 2),
(26, 2),
(27, 2),
(28, 2),
(29, 2),
(30, 2),
(3, 3),
(7, 3),
(8, 3),
(15, 3),
(16, 3),
(17, 3),
(18, 3),
(4, 4),
(9, 4),
(10, 4),
(19, 4),
(20, 4),
(21, 4),
(22, 4),
(5, 5),
(11, 5),
(12, 5),
(23, 5),
(24, 5),
(25, 5),
(26, 5),
(6, 6),
(13, 6),
(14, 6),
(27, 6),
(28, 6),
(29, 6),
(30, 6),
(7, 7),
(15, 7),
(16, 7),
(8, 8),
(17, 8),
(18, 8),
(9, 9),
(19, 9),
(20, 9),
(10, 10),
(21, 10),
(22, 10),
(11, 11),
(23, 11),
(24, 11),
(12, 12),
(25, 12),
(26, 12),
(13, 13),
(27, 13),
(28, 13),
(14, 14),
(29, 14),
(30, 14),
(15, 15),
(16, 16),
(17, 17),
(18, 18),
(19, 19),
(20, 20),
(21, 21),
(22, 22),
(23, 23),
(24, 24),
(25, 25),
(26, 26),
(27, 27),
(28, 28),
(29, 29),
(30, 30);
--
-- Indexes for dumped tables
--
--
-- Indexes for table `category_name`
--
ALTER TABLE `category_name`
ADD PRIMARY KEY (`id`);
--
-- Indexes for table `tree_path`
--
ALTER TABLE `tree_path`
ADD PRIMARY KEY (`children`,`parent`),
ADD KEY `FK_PARENT` (`parent`);
--
-- AUTO_INCREMENT for dumped tables
--
--
-- AUTO_INCREMENT for table `category_name`
--
ALTER TABLE `category_name`
MODIFY `id` bigint NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=31;
--
-- Constraints for dumped tables
--
--
-- Constraints for table `tree_path`
--
ALTER TABLE `tree_path`
ADD CONSTRAINT `FK_CHILDREN` FOREIGN KEY (`children`) REFERENCES `category_name` (`id`) ON DELETE CASCADE,
ADD CONSTRAINT `FK_PARENT` FOREIGN KEY (`parent`) REFERENCES `category_name` (`id`) ON DELETE CASCADE;
COMMIT;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;