无法更新DynamoDB中的项目

Question

我一直在试图弄清楚如何更新dynamoDB中的项目，但没有取得任何成功。

我知道如何添加和设置和删除项目但不更新。

这是我的代码：

dynamoDB.updateItem({
    "TableName": "mytable",
    "Key": {
        "thing_ID": {"S": "0000"}
    },
    "UpdateExpression": "SET",
    "ExpressionAttributeNames": {
        "SessionID": ""
    },
    "ExpressionAttributeValues": {
        "SessionID": {
            "S": "maybe this works",
        }
    }
})

Answer 1

看起来您正在尝试使用Expression更新项目，在这种情况下，您的UpdateExpression不正确。 ExpressionAttributeNames和ExpressionAttributeValues都用于ExpressionAttributeValues中的占位符替换 。

如果您想为项目设置属性，我认为您的代码看起来像这样：

dynamoDB.updateItem({  
    "TableName" : "exampleTable",
    "Key" : {
        "hashAttributeName" : {
            "S" : "thing_ID"
        }
    },
    "UpdateExpression" : "SET #attrName =:attrValue",
    "ExpressionAttributeNames" : {
        "#attrName" : "SessionID"
    },
    "ExpressionAttributeValues" : {
        ":attrValue" : {
            "S" : "maybe this works"
        }
    }
});

这将更新一个如下所示的项：

{  
    "Item":{  
        "hashAttributeName":"thing_ID"
    }
}

对此：

{  
    "Item":{  
        "hashAttributeName" : "thing_ID",
        "SessionID" : "maybe this works"
    }
}

Answer 2

以下是使用AWS SDK for JavaScript v2.1.33的示例。

完整的示例如下： https ： //github.com/mayosmith/HelloDynamoDB/blob/master/HelloDynamoDB.html

/*
-----------------------------------------------------------------
AWS configure
Note: this is a simple experiement for demonstration
purposes only. Replace the keys below with your own.
Do not include the secret key in an actual production
environment, because, then, it wont be secret anymore...
-----------------------------------------------------------------
*/
AWS.config.update({accessKeyId: 'AKIAJUPWRIYYQGDB6AFA', secretAccessKey: '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'});
// Configure the region
AWS.config.region = 'us-west-2';  //us-west-2 is Oregon
//create the ddb object
var ddb = new AWS.DynamoDB();
/*
-----------------------------------------------------------------
Update the Table
-----------------------------------------------------------------
*/
//update the table with this data
var params = {
  Key: {
    name: {S: 'John Mayo-Smith'},
    city: {S: 'New York'}
  },
  AttributeUpdates: {
    food: {
      Action: 'PUT',
      Value: {S: 'chocolate'}
    }
  },
  TableName: 'sampletable',
  ReturnValues: 'ALL_NEW'
};
//update the table
update();
/*
-----------------------------------------------------------------
Get Item from the Table
-----------------------------------------------------------------
*/
//attribute to read
var readparams = {

  Key: {
    name: {S: 'John Mayo-Smith'},
    city: {S: 'New York'}
  },
  AttributesToGet: ['food'],
  TableName: 'sampletable'
};
//get the item
read();
/*
-----------------------------------------------------------------
function update()
Description: Calls updateItem which is part of the AWS Javascript
SDK.
Returns: JSON object (the object is stringifyed so we can see 
what's going on in the javascript console)
-----------------------------------------------------------------
*/
function update(){
    ddb.updateItem(params, function(err, data) {
        if (err) { return console.log(err); }
        console.log("We updated the table with this: " + JSON.stringify(data));
    });
}
/*
-----------------------------------------------------------------
function read()
Description: Calls getItem which is part of the AWS Javascript
SDK.
Returns: JSON object (the object is stringifyed so we can see 
what's going on in the javascript console)
-----------------------------------------------------------------
*/
function read(){
    ddb.getItem(readparams, function(err, data) {
        if (err) { return console.log(err); }
        console.log(": " + data);       

    console.log("John's favorite food is: "+ JSON.stringify(data.Item.food.S)); // print the item data
});
}

Answer 3

下面的代码对我有用，尝试一次

 var item = {"endTime": "7pm", "imageName": "7abcd", "startTime": "7pm"};

dynamo.updateItem({
TableName:'tableName',
Key:{"primaryKey":"primaryKeyValue"},
AttributeUpdates: { images: { Action: "ADD", Value: item } }},function(err, data) {
    if (err)
        console.log(err);
    else
        console.log(data)
});