{
  "id": "python/flask-sqlalchemy-connection-error",
  "signature": "sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, \"Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)\")",
  "signature_zh": "SQLAlchemy操作错误：无法连接到MySQL服务器",
  "regex": "sqlalchemy\\.exc\\.OperationalError:\\ \\(pymysql\\.err\\.OperationalError\\)\\ \\(2003,\\ \"Can't\\ connect\\ to\\ MySQL\\ server\\ on\\ 'localhost'\\ \\(\\[Errno\\ 111\\]\\ Connection\\ refused\\)\"\\)",
  "domain": "python",
  "category": "network_error",
  "subcategory": null,
  "root_cause": "Flask-SQLAlchemy无法连接到数据库服务器，可能是服务未运行或配置错误",
  "root_cause_type": "generic",
  "root_cause_zh": "Flask-SQLAlchemy无法连接到数据库服务器，可能是服务未运行或配置错误",
  "versions": [
    {
      "version": "3.x",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "尝试使用不同的数据库驱动",
      "why_fails": "连接问题通常是服务器或网络问题，不是驱动问题",
      "fail_rate": 0.5,
      "condition": "",
      "sources": []
    },
    {
      "action": "修改数据库URL但忽略端口",
      "why_fails": "端口错误会导致连接失败",
      "fail_rate": 0.4,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "确保数据库服务正在运行",
      "success_rate": 0.9,
      "how": "sudo systemctl start mysql",
      "condition": "",
      "sources": []
    },
    {
      "action": "检查数据库连接配置",
      "success_rate": 0.95,
      "how": "app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://user:pass@localhost:3306/db'",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": null,
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.85,
  "fix_success_rate": 0.8,
  "resolvable": "true",
  "first_seen": "2024-04-10",
  "last_confirmed": "2025-01-01",
  "last_updated": "2025-01-01",
  "evidence_count": 0,
  "tags": [],
  "locale": "en",
  "aliases": []
}