困惑于查询DynamoDB

我的DynamoDB中有以下数据。困惑于查询DynamoDB

，我试图达到如下的结果。扫描整个表格并获取management is NULL and Location is Midwest所在的行。

我最初尝试以下查询以匹配Null。

var scanningParameters = { 
    TableName: 'LOB', 
    FilterExpression: "#mgmt contains NULL", 
    ExpressionAttributeNames: { 
     "#mgmt": "Management", 
    } 
}; 

docClient.scan(scanningParameters, onScan); 
function onScan(err, data) { 
    if (err) { 
     console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2)); 
    } else { 
     // print all the movies 
     console.log("Scan succeeded."); 
     data.Items.forEach(function (data) { 
      console.log(
       data.lineofbusiness + " name : ", 
       data.name); 
     }); 

     if (typeof data.LastEvaluatedKey != "undefined") { 
      console.log("Scanning for more..."); 
      scanningParameters.ExclusiveStartKey = data.LastEvaluatedKey; 
      docClient.scan(scanningParameters, onScan); 
     } 
    } 
}

我得到的异常，因为

{ 
    "message": "Invalid FilterExpression: Syntax error; token: \"contains\", near: \"#mgmtcontains NULL\"", 
    "code": "ValidationException", 
    "time": "2017-05-03T13:21:11.611Z", 
    "requestId": "0T0GU59HRJ24P96D42H9QNC97RVV4KQNSO5AEMVJF66Q9ASUAAJG", 
    "statusCode": 400, 
    "retryable": false, 
    "retryDelay": 13.73953651636839 
}

请让我知道我要去哪里错了，我怎么能解决这个问题。

来源

2017-05-03 user3872094

我假设你有管理的价值为NULL属性 – notionquest

是在管理该值为NULL – user3872094

即使扫描是足够好，我可以得到休息 – user3872094

以下是“NULL”值（即具有NULL作为数据的String属性）的扫描项目。

我假设Management属性是包含字符串值“NULL”的String数据类型。

代码： -

var AWS = require("aws-sdk"); 
var creds = new AWS.Credentials('akid', 'secret', 'session'); 

AWS.config.update({ 
    region: "us-west-2", 
    endpoint: "http://localhost:8000", 
    credentials : creds 
}); 

var docClient = new AWS.DynamoDB.DocumentClient(); 

var params = { 
    TableName: "lob", 
    FilterExpression: "#mgmt = :mgmtVal", 
    ExpressionAttributeNames: { 
     "#mgmt": "Management", 
    }, 
    ExpressionAttributeValues : { 
     ":mgmtVal" : "NULL" 
    } 
}; 

docClient.scan(params, onScan); 
var count = 0; 

function onScan(err, data) { 
    if (err) { 
     console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2)); 
    } else { 
     console.log("Scan succeeded."); 
     data.Items.forEach(function(itemData) { 
      console.log("Item :", ++count,JSON.stringify(itemData)); 
     }); 

     if (typeof data.LastEvaluatedKey != "undefined") { 
      params.ExclusiveStartKey = data.LastEvaluatedKey; 
      docClient.scan(params, onScan); 
     } 
    } 
}

来源

2017-05-03 13:52:45 notionquest

困惑于查询DynamoDB

回答

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