249 lines
5.8 KiB
Markdown
249 lines
5.8 KiB
Markdown
# Banner批量排序SQL语法Bug修复报告
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## 🐛 问题描述
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### 错误信息
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```
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SQLSyntaxErrorException: You have an error in your SQL syntax;
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check the manual that corresponds to your MySQL server version for the right syntax to use near
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'UPDATE banner SET sort_order = 2, update_time =' at line 6
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```
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### 错误位置
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- **方法**: `BannerMapper.batchUpdateSortOrder`
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- **文件**: `BannerMapper.xml`
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- **操作**: 批量更新Banner排序
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---
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## 🔍 根本原因分析
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### 问题SQL语法
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```xml
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<!-- ❌ 错误的SQL语法 -->
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<update id="batchUpdateSortOrder">
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<foreach collection="banners" item="banner" separator=";">
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UPDATE banner SET
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sort_order = #{banner.sortOrder},
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update_time = NOW()
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WHERE id = #{banner.id}
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</foreach>
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</update>
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```
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### 生成的错误SQL
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```sql
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UPDATE banner SET sort_order = ?, update_time = NOW() WHERE id = ? ;
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UPDATE banner SET sort_order = ?, update_time = NOW() WHERE id = ? ;
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UPDATE banner SET sort_order = ?, update_time = NOW() WHERE id = ? ;
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...
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```
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### 问题原因
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1. **多语句分隔**: 使用分号分隔多个UPDATE语句
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2. **MySQL限制**: MySQL的PreparedStatement不支持多语句执行
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3. **MyBatis误用**: `separator=";"` 不适用于UPDATE操作
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---
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## ✅ 修复方案
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### 新的SQL实现
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```xml
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<!-- ✅ 正确的SQL语法 -->
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<update id="batchUpdateSortOrder">
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UPDATE banner
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SET sort_order = CASE
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<foreach collection="banners" item="banner">
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WHEN id = #{banner.id} THEN #{banner.sortOrder}
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</foreach>
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ELSE sort_order
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END,
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update_time = NOW()
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WHERE id IN
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<foreach collection="banners" item="banner" open="(" separator="," close=")">
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#{banner.id}
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</foreach>
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</update>
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```
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### 生成的正确SQL
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```sql
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UPDATE banner
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SET sort_order = CASE
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WHEN id = 1 THEN 5
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WHEN id = 2 THEN 2
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WHEN id = 3 THEN 3
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WHEN id = 4 THEN 4
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WHEN id = 5 THEN 1
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ELSE sort_order
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END,
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update_time = NOW()
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WHERE id IN (1, 2, 3, 4, 5)
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```
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---
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## 📊 修复前后对比
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### 修复前
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| 问题 | 影响 |
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|------|------|
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| ❌ 多语句UPDATE分隔 | 语法错误，无法执行 |
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| ❌ 使用分号分隔符 | MySQL PreparedStatement不支持 |
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| ❌ 执行失败 | 批量排序功能无法使用 |
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### 修复后
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| 改进 | 效果 |
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|------|------|
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| ✅ 单一CASE WHEN UPDATE | 标准SQL语法，完全兼容 |
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| ✅ 批量条件更新 | 一次执行更新多个记录 |
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| ✅ 高效执行 | 比多次单独UPDATE更快 |
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---
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## 🧪 测试验证
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### 测试数据示例
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```javascript
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// 批量排序数据
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[
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{"id": 1, "sortOrder": 5},
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{"id": 2, "sortOrder": 2},
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{"id": 3, "sortOrder": 3},
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{"id": 4, "sortOrder": 4},
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{"id": 5, "sortOrder": 1}
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]
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```
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### 生成的SQL验证
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```sql
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UPDATE banner
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SET sort_order = CASE
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WHEN id = 1 THEN 5
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WHEN id = 2 THEN 2
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WHEN id = 3 THEN 3
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WHEN id = 4 THEN 4
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WHEN id = 5 THEN 1
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ELSE sort_order
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END,
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update_time = NOW()
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WHERE id IN (1, 2, 3, 4, 5)
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```
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### 预期结果
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- ✅ SQL语法正确，可以正常执行
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- ✅ 所有指定ID的记录都会更新排序值
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- ✅ 未指定的记录保持原有排序值不变
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- ✅ 所有记录的 `update_time` 都会更新
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---
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## 🛡️ SQL最佳实践
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### 1. 批量更新策略
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```sql
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-- ✅ 推荐：使用CASE WHEN进行批量更新
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UPDATE table_name
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SET column1 = CASE
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WHEN condition1 THEN value1
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WHEN condition2 THEN value2
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ELSE column1
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END
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WHERE id IN (id_list);
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-- ❌ 避免：多语句分隔
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UPDATE table SET col=val WHERE id=1;
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UPDATE table SET col=val WHERE id=2;
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```
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### 2. MyBatis批量操作
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```xml
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<!-- ✅ 正确的批量更新 -->
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<update id="batchUpdate">
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UPDATE table SET field = CASE
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<foreach collection="list" item="item">
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WHEN id = #{item.id} THEN #{item.value}
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</foreach>
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ELSE field
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END
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WHERE id IN
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<foreach collection="list" item="item" open="(" separator="," close=")">
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#{item.id}
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</foreach>
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</update>
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<!-- ❌ 错误的多语句方式 -->
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<update id="batchUpdateWrong">
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<foreach collection="list" item="item" separator=";">
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UPDATE table SET field = #{item.value} WHERE id = #{item.id}
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</foreach>
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</update>
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```
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### 3. 性能优势
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| 方式 | SQL语句数 | 网络往返 | 事务处理 |
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|------|-----------|----------|----------|
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| **CASE WHEN批量** | 1条 | 1次 | 原子操作 |
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| **多次单独UPDATE** | N条 | N次 | 需要显式事务 |
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---
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## 📋 文件变更清单
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### 修改文件
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- ✅ `src/main/resources/mapper/BannerMapper.xml` - 修复 `batchUpdateSortOrder` SQL语法
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### 新增文件
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- ✅ `docs/banner-batch-sort-bug-fix.md` - 本修复报告
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---
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## 🎯 修复效果
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### ✅ 解决的问题
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1. **SQL语法错误**: 消除了多语句分隔导致的语法错误
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2. **执行效率**: 从多次UPDATE改为单次批量UPDATE
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3. **事务安全**: 确保批量操作的原子性
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4. **代码质量**: 使用标准的SQL批量更新模式
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### 🚨 注意事项
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1. **测试验证**: 确保批量排序功能正常工作
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2. **性能监控**: 观察批量更新的执行时间
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3. **数据一致性**: 验证所有记录都正确更新
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---
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## 🧪 测试建议
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### 使用测试页面验证
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1. 访问 `/test_banner_admin.html`
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2. 点击"获取Banner列表"加载数据
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3. 点击"测试批量排序"生成随机排序
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4. 点击"批量更新排序"执行更新
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5. 重新加载列表验证排序是否正确
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### 命令行测试
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```bash
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# 测试批量排序接口
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curl -X PUT "http://localhost:8081/admin/banners/batch-sort" \
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-H "Authorization: Bearer {admin_token}" \
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-H "Content-Type: application/json" \
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-d '[{"id":1,"sortOrder":5},{"id":2,"sortOrder":2}]'
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```
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---
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**修复状态**: ✅ 已完成
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**测试状态**: ⏳ 待验证
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**风险等级**: 低（只影响批量排序功能）
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**部署要求**: 重启服务器使MyBatis配置生效
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