# ImportError: 没有名为 'flask_sqlalchemy' 的模块

- **ID:** `python/flask-import-error-flask-sqlalchemy-not-installed`
- **领域:** python
- **类别:** module_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

环境中未安装 Flask-SQLAlchemy 扩展。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 3.x | active | — | — |

## 解决方案

1. **Install Flask-SQLAlchemy** (95% 成功率)
   ```
   pip install flask-sqlalchemy
# Then import: from flask_sqlalchemy import SQLAlchemy
   ```
2. **Use virtual environment and install** (90% 成功率)
   ```
   python -m venv venv
source venv/bin/activate
pip install flask flask-sqlalchemy
   ```

## 无效尝试

- **Installing with pip install flask-sqlalchemy but using wrong import name** — Import name is flask_sqlalchemy, not flask-sqlalchemy. (70% 失败率)
- **Assuming it's included with Flask** — Flask-SQLAlchemy is a separate package. (80% 失败率)