Question

代码无法识别列别名

我正在使用PowerShell（sqlcmd）测试代码，并且代码返回错误，它无法识别第3行中的“日期”列？我在第1列中定义了“日期”，所以我很困惑，请问有人，因为我是SQL新手。

SELECT DATEADD(dd,0, DATEDIFF(dd,0, MyDate)) AS SDate
FROM Schedule
WHERE Sdate > '20180101';

Answer 1

这是SQL不允许您使用别名的方式。重复“功能”

改为

Resources:
  IAMRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Action: ['sts:AssumeRole']
            Effect: Allow
            Principal:
              Service: [lambda.amazonaws.com]
        Version: 2012-10-17
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: lambda.handler
      Role: !GetAtt IAMRole.Arn
      Runtime: ruby2.5
      CodeUri: "./src/"
      MemorySize: 512
      Timeout: 30
      Events:
        MyAppApi:
            Type: Api
            Properties:
                Path: /
                Method: ANY
                RestApiId: !Ref MyAppAPI
  MyAppAPI:
    Type: AWS::Serverless::Api
    Properties:
      Name: MyAppAPI
      StageName: Prod
      DefinitionBody:
        swagger: '2.0'
        basePath: '/'
        info:
          title: !Ref AWS::StackName
        paths:
          /{proxy+}:
            x-amazon-apigateway-any-method:
              responses: {}
              x-amazon-apigateway-integration:
                uri:
                  !Sub 'arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyFunction.Arn}/invocations'
                passthroughBehavior: "when_no_match"
                httpMethod: POST
                type: "aws_proxy"
          /:
            post:
              responses: {}
              x-amazon-apigateway-integration:
                uri:
                  !Sub 'arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyFunction.Arn}/invocations'
                passthroughBehavior: "when_no_match"
                httpMethod: POST
                type: "aws_proxy"
  ConfigLambdaPermission:
    Type: "AWS::Lambda::Permission"
    DependsOn:
    - MyFunction
    Properties:
      Action: lambda:InvokeFunction
      FunctionName: !Ref MyFunction
      Principal: apigateway.amazonaws.com
  ConfigLambdaPermission:
    Type: "AWS::Lambda::Permission"
    DependsOn:
    - MyFunction
    Properties:
      Action: lambda:InvokeFunction
      FunctionName: !Ref MyFunction
      Principal: !GetAtt IAMRole.Arn

Outputs:
  MyFunction:
    Description: Lambda Function for interacting with Slack
    Value:
      Fn::GetAtt:
      - MyFunction
      - Arn
  MyAppAppUrl:
    Description: App endpoint URL
    Value: !Sub "https://${MyAppAPI}.execute-api.${AWS::Region}.amazonaws.com/"

Answer 2

WHERE在SELECT之前进行评估。这就是Sdate无法识别的原因。 SQL操作顺序

FROM WHERE GROUP BY HAVING WINDOW functions SELECT DISTINCT UNION ORDER BY LIMIT and OFFSET

Answer 3

别名不支持where中的所有dbms

SELECT DATEADD(dd,0, DATEDIFF(dd,0, MyDate)) AS SDate
    FROM Schedule
    WHERE MyDate> '20180101'

SQL无法识别命名列

3 个答案: