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379 lines
9.3 KiB
Markdown
379 lines
9.3 KiB
Markdown
# 知识点DELETE语句未能删除全部记录的原因分析
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**问题SQL**：
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```sql
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DELETE FROM knowledge_points WHERE material_id = 34;
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```
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**问题描述**：用户反馈该SQL语句未能删除资料34的全部知识点
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---
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## 🔍 问题分析
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### 1. 数据现状
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资料34当前有6个知识点记录：
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| ID | 知识点名称 | is_deleted | 创建时间 |
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|----|-----------|------------|----------|
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| 1142 | FAB法则介绍 | 0 | 2025-10-17 07:20:28 |
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| 1143 | 全面有效的抗衰需求满足 | 0 | 2025-10-17 07:20:28 |
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| 1144 | 能量聚焦与精准技术 | 0 | 2025-10-17 07:20:28 |
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| 1145 | 多层次治疗与专利炮头 | 0 | 2025-10-17 07:20:28 |
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| 1146 | 国内首款医美合规超声刀的安全性与合规性 | 0 | 2025-10-17 07:20:28 |
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| 1147 | 提升舒适度与减少副作用 | 0 | 2025-10-17 07:20:28 |
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### 2. 表结构分析
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```sql
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CREATE TABLE `knowledge_points` (
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`id` int NOT NULL AUTO_INCREMENT,
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`course_id` int DEFAULT NULL COMMENT '所属课程ID',
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`material_id` int NOT NULL COMMENT '关联资料ID（必填）',
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`name` varchar(200) NOT NULL COMMENT '知识点名称',
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`description` text COMMENT '知识点描述',
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`is_deleted` tinyint(1) DEFAULT '0' COMMENT '是否删除', -- ⚠️ 软删除字段
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`deleted_at` datetime DEFAULT NULL COMMENT '删除时间',
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`created_by` int DEFAULT NULL,
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`updated_by` int DEFAULT NULL,
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`created_at` datetime DEFAULT CURRENT_TIMESTAMP,
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`updated_at` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
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`type` varchar(50) DEFAULT '理论知识',
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`source` tinyint(1) DEFAULT '0',
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`topic_relation` varchar(200) DEFAULT NULL,
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PRIMARY KEY (`id`),
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KEY `idx_course_id` (`course_id`),
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KEY `idx_is_deleted` (`is_deleted`),
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KEY `material_id` (`material_id`),
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CONSTRAINT `knowledge_points_ibfk_1` FOREIGN KEY (`course_id`)
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REFERENCES `courses` (`id`) ON DELETE CASCADE,
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CONSTRAINT `knowledge_points_ibfk_2` FOREIGN KEY (`material_id`)
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REFERENCES `course_materials` (`id`) ON DELETE CASCADE
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);
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```
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**关键发现**：
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- ✅ 表中有 `is_deleted` 字段 → **系统使用软删除机制**
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- ✅ material_id有外键约束，ON DELETE CASCADE
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- ✅ course_id有外键约束，ON DELETE CASCADE
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### 3. 外键约束检查
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```sql
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-- exam_mistakes表引用knowledge_points
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CONSTRAINT exam_mistakes_ibfk_4
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FOREIGN KEY (knowledge_point_id)
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REFERENCES knowledge_points(id)
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ON DELETE SET NULL
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```
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**检查结果**：
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- ✅ 没有错题记录引用资料34的知识点
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- ✅ DELETE_RULE是SET NULL，不会阻止删除
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---
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## ❌ 问题根因
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### 核心问题：系统使用软删除，但SQL使用了物理删除
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**系统设计**：
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- 后端代码使用 `soft_delete()` 方法，将 `is_deleted` 设置为1
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- 前端查询时使用 `WHERE is_deleted = 0` 筛选未删除的记录
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- 所有删除操作都是软删除，不会真正从数据库删除记录
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**用户执行的SQL**：
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```sql
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DELETE FROM knowledge_points WHERE material_id = 34; -- ❌ 物理删除
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```
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**为什么"未能删除全部知识点"**：
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有以下几种可能原因：
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#### 原因1：SQL实际上执行成功了（最可能）
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- ✅ DELETE语句执行成功，记录被物理删除
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- ✅ 但之后系统又重新创建了这些知识点
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- 🔍 需要检查是否有后台任务或自动同步机制
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#### 原因2：未提交事务
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```sql
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-- 如果在事务中执行但未提交
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START TRANSACTION;
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DELETE FROM knowledge_points WHERE material_id = 34;
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-- 未执行 COMMIT
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```
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#### 原因3：没有执行权限
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- 用户可能没有DELETE权限
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- 需要检查用户权限
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#### 原因4：有触发器或其他机制
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- 可能有BEFORE DELETE或AFTER DELETE触发器阻止删除
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- 需要检查触发器
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---
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## ✅ 正确的删除方法
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### 方法1：使用系统的软删除（推荐）
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**后端API方式**：
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```bash
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# 通过后端API删除（软删除）
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curl -X DELETE "https://aiedu.ireborn.com.cn/api/v1/courses/materials/34/knowledge-points/{knowledge_point_id}" \
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-H "Authorization: Bearer {token}"
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```
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**直接SQL方式（软删除）**：
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```sql
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-- 软删除资料34的所有知识点
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UPDATE knowledge_points
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SET is_deleted = 1,
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deleted_at = NOW()
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WHERE material_id = 34
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AND is_deleted = 0;
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```
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### 方法2：删除资料（级联删除知识点）
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```sql
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-- 软删除资料，知识点会通过外键级联删除
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UPDATE course_materials
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SET is_deleted = 1,
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deleted_at = NOW()
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WHERE id = 34
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AND is_deleted = 0;
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```
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### 方法3：物理删除（谨慎使用）
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**⚠️ 警告**：物理删除会永久删除数据，无法恢复！
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```sql
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-- 如果确实需要物理删除
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DELETE FROM knowledge_points WHERE material_id = 34;
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-- 验证删除结果
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SELECT COUNT(*) FROM knowledge_points WHERE material_id = 34;
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-- 应该返回 0
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```
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---
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## 🔍 排查步骤
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### 1. 检查记录是否真的还在
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```sql
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-- 查看记录数量
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SELECT COUNT(*) as total_count
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FROM knowledge_points
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WHERE material_id = 34;
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-- 查看详细记录
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SELECT id, name, is_deleted, deleted_at
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FROM knowledge_points
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WHERE material_id = 34
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ORDER BY id;
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```
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### 2. 检查事务状态
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```sql
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-- 查看当前未提交的事务
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SELECT * FROM information_schema.INNODB_TRX;
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-- 如果有未提交的事务，提交或回滚
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COMMIT;
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-- 或
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ROLLBACK;
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```
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### 3. 检查触发器
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```sql
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-- 查看knowledge_points表的触发器
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SHOW TRIGGERS LIKE 'knowledge_points';
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```
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### 4. 检查删除权限
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```sql
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-- 查看当前用户权限
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SHOW GRANTS FOR 'root'@'%';
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-- 或查看当前会话权限
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SHOW GRANTS FOR CURRENT_USER;
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```
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### 5. 验证外键约束
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```sql
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-- 禁用外键检查（谨慎使用）
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SET FOREIGN_KEY_CHECKS = 0;
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-- 执行删除
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DELETE FROM knowledge_points WHERE material_id = 34;
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-- 重新启用外键检查
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SET FOREIGN_KEY_CHECKS = 1;
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-- 验证结果
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SELECT COUNT(*) FROM knowledge_points WHERE material_id = 34;
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```
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---
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## 📝 推荐操作流程
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### 场景A：想要"隐藏"知识点（软删除）✅ 推荐
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```sql
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-- 1. 软删除知识点
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UPDATE knowledge_points
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SET is_deleted = 1,
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deleted_at = NOW(),
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updated_by = {user_id} -- 记录操作人
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WHERE material_id = 34
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AND is_deleted = 0;
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-- 2. 验证结果
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SELECT COUNT(*) as deleted_count
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FROM knowledge_points
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WHERE material_id = 34
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AND is_deleted = 1;
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-- 3. 前端查询时会自动过滤
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-- SELECT * FROM knowledge_points WHERE material_id = 34 AND is_deleted = 0;
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-- 返回 0 条记录
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```
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### 场景B：需要永久删除记录（物理删除）⚠️ 谨慎
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```sql
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-- 1. 备份数据（重要！）
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CREATE TABLE knowledge_points_backup_20251017 AS
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SELECT * FROM knowledge_points WHERE material_id = 34;
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-- 2. 检查依赖关系
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SELECT COUNT(*) as dependent_count
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FROM exam_mistakes
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WHERE knowledge_point_id IN (
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SELECT id FROM knowledge_points WHERE material_id = 34
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);
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-- 3. 执行物理删除
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DELETE FROM knowledge_points WHERE material_id = 34;
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-- 4. 验证结果
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SELECT COUNT(*) FROM knowledge_points WHERE material_id = 34;
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-- 应该返回 0
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-- 5. 提交事务
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COMMIT;
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```
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---
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## 🎯 解决方案总结
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### 如果要删除资料34的全部知识点：
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**✅ 推荐：通过后端API删除资料**
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```bash
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# 这会软删除资料及其所有知识点
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curl -X DELETE "https://aiedu.ireborn.com.cn/api/v1/courses/{course_id}/materials/34" \
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-H "Authorization: Bearer {token}"
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```
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**✅ 次选：SQL软删除**
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```sql
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-- 软删除所有知识点
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UPDATE knowledge_points
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SET is_deleted = 1, deleted_at = NOW()
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WHERE material_id = 34 AND is_deleted = 0;
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```
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**⚠️ 不推荐：SQL物理删除**
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```sql
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-- 永久删除（不可恢复）
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DELETE FROM knowledge_points WHERE material_id = 34;
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COMMIT; -- 记得提交事务！
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```
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---
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## 🔧 故障排除
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### 如果DELETE语句执行后记录仍然存在：
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1. **检查事务是否提交**
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```sql
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COMMIT;
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```
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2. **检查是否在错误的数据库**
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```sql
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SELECT DATABASE();
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-- 应该返回 kaopeilian
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```
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3. **检查WHERE条件是否正确**
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```sql
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SELECT COUNT(*) FROM knowledge_points WHERE material_id = 34;
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-- 执行DELETE前应该有记录
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```
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4. **查看MySQL错误日志**
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```bash
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docker exec kaopeilian-mysql-dev tail -100 /var/log/mysql/error.log
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```
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5. **测试简单的DELETE**
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```sql
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-- 删除单条记录测试
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DELETE FROM knowledge_points WHERE id = 1142 LIMIT 1;
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SELECT * FROM knowledge_points WHERE id = 1142;
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```
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---
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## 📚 相关文档
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- 数据库架构：`/root/aiedu/kaopeilian-backend/数据库架构-统一版.md`
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- Service层代码：`/root/aiedu/kaopeilian-backend/app/services/course_service.py`
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- Base Service：`/root/aiedu/kaopeilian-backend/app/services/base_service.py`
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---
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## 💡 经验教训
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1. **理解系统的删除机制**
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- 软删除系统中，直接使用DELETE可能导致数据不一致
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- 应该使用系统提供的API或软删除SQL
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2. **谨慎使用物理删除**
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- 物理删除是不可逆的
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- 删除前应该备份数据
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- 检查是否有外键依赖
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3. **使用事务**
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- 重要的删除操作应该在事务中进行
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- 先验证后提交
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4. **记录操作日志**
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- 删除操作应该记录操作人和操作时间
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- 便于追溯和审计
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---
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**结论**：用户的DELETE语句从语法上是正确的，能够执行。如果执行后记录仍然存在，最可能的原因是：
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1. 事务未提交
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2. 后台任务重新创建了记录
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3. 在错误的数据库环境执行
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建议使用软删除而不是物理删除，以保持系统一致性。
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