尝试连接到 MySQL 数据库时出现“db is not defined”错误[关闭]

Posted 2023-03-07

【中文标题】尝试连接到 MySQL 数据库时出现“db is not defined”错误[关闭]

【英文标题】："db is not defined" error when trying to connect to MySQL database [closed]

【发布时间】：2021-09-27 18:35:11

【问题描述】：

我正在尝试使用 Node.JS 构建 AWS Lambda 函数。这是我的代码。我是 Node.JS 的超级新手。

var response;

var mysql = require('mysql');
var con = mysql.createConnection(
    host: "*****.rds.amazonaws.com",
    user: "****",
    password: "***",
    database: "***",
    port: 3306
); 
    

exports.lambdaHandler = async (event, context) => 

    con.connect();

    try
        db.query( 'SELECT * from accounting_type' ).then( rows => 
            response = 
                'statusCode': 200,
                'body': JSON.stringify(
                    rows,
                )
            
           );
    
    catch(err)
    
        console.log(err);
        response = 
            'statusCode': 200,
            'body': JSON.stringify(
                err,
            )
        
    
    return response;

;

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  node2

  Sample SAM Template for node2
  
# More info about Globals: https://github.com/awslabs/serverless-application-model/blob/master/docs/globals.rst
Globals:
  Function:
    Timeout: 3

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      Events:
        HelloWorld:
          Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
          Properties:
            Path: /hello
            Method: get
      Role: !GetAtt LambdaRole.Arn
      VpcConfig:
        SecurityGroupIds:
          - sg-041f2459dcd921e8e
        SubnetIds:
          - subnet-0456db2d
          - subnet-c6414cb
 
  LambdaRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Path: /
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      Policies:
        - PolicyName: root
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Effect: Allow
                Action:
                  - ec2:DescribeNetworkInterfaces
                  - ec2:CreateNetworkInterface
                  - ec2:DeleteNetworkInterface
                  - ec2:DescribeInstances
                  - ec2:AttachNetworkInterface
                Resource: '*'

执行时，代码返回以下错误

START RequestId: 026dc152-40d0-49d3-b764-ded5f0cbc2b7 Version: $LATEST
2021-07-20T08:01:48.401Z    026dc152-40d0-49d3-b764-ded5f0cbc2b7    INFO    ReferenceError: db is not defined
    at Runtime.exports.lambdaHandler [as handler] (/var/task/app.js:20:9)
    at Runtime.handleOnce (/var/runtime/Runtime.js:66:25)
END RequestId: 026dc152-40d0-49d3-b764-ded5f0cbc2b7
REPORT RequestId: 026dc152-40d0-49d3-b764-ded5f0cbc2b7  Duration: 1609.64 ms    Billed Duration: 1610 ms    Memory Size: 128 MB Max Memory Used: 80 MB  Init Duration: 152.15 ms    
XRAY TraceId: 1-60f682ea-66ea5e370df8860b12cf43fd   SegmentId: 5d2fad42374469c0 Sampled: true

【参考方案1】：

您将 mysql 连接游标分配给 con 变量并在查询中使用 db，因此 db 未定义。将 db 替换为 con，如下所示：

con.query( 'SELECT * from accounting_type' , (err,rows) => 
            if(err)
               console.error(err)
               return
            
            response = 
                'statusCode': 200,
                'body': JSON.stringify(
                    rows,
                )
            
          );

更新了使用 (err,rows) 回调而不是 .then 的答案，因为 .then 根据文档不可用。

【讨论】：

谢谢，现在我收到TypeError: con.query(...).then is not a function

根据文档，查询具有 err 和 rows 值的回调。尝试这样做：con.query('SELECT * FROM accounting_type', (err,rows) => ... ) 请查看文档以获取更多详细信息。

【参考方案2】：

这是因为您将引用的内容定义为 db 为 con，如下所示：

var con = mysql.createConnection(
    host: "*****.rds.amazonaws.com",
    user: "****",
    password: "***",
    database: "***",
    port: 3306
);

请更新您的代码，将con 替换为db，或将db 替换为con

【讨论】：

谢谢。现在我收到错误TypeError: con.query(...).then is not a function