使用Boto3实现的Lambda函数更新DynamoDB表的值

问题描述

我正在尝试使用我的API方法来实现更新操作，以更新表的内容.

I am trying to achieve an update operation using my API method to update the content of the table.

我设置了以下lambda代码:

I have following lambda code set up:

def lambda_handler(event, context):
    param = event['queryStringParameters']['employeID']
     name = event['queryStringParameters']['employeName']
    dynamodb = boto3.resource('dynamodb', region_name="us-east-1")
    table = dynamodb.Table('api_demo_employe')

    response = table.update_item(
        Key = {
            'employeID' : param
        }

        )

我需要弄清楚如何使用我的更新变量设置 UpdateExpression，ConditionExpression，ExpressionAttributeValues .

I need to figure out how can i set the UpdateExpression,ConditionExpression, ExpressionAttributeValues using my update variable.

有人可以帮我吗?

推荐答案

会是这样的:

response = table.update_item(TableName=table,
                             ReturnValues='UPDATED_NEW',
                             Key={'employeID': {'S': param}},
                             ExpressionAttributeValues={':f': {'S': update['some_param']},
                                                     ':limit': {'N': '500'}},
                             UpdateExpression='SET some_field = :f',
                             ConditionExpression='some_other_field > :limit'
                            )

当然，这只是一个例子-您的特定表达式将取决于您要执行的操作.我正在猜测您的数据类型.'S'用于字符串，但是其他数据类型还有其他选项.您可以在 ExpressionAttributeValues 中定义替换变量，然后根据需要在 UpdateExpression 和 ConditionExpression 中引用它们.

Of course this is just an example--your specific expressions will depend on what you are trying to do. And I am guessing at your data types. The 'S' is for a string, but there are other options for other data types. You define the substitution variables in ExpressionAttributeValues and then reference those in the UpdateExpression and ConditionExpression as needed.

有关所有选项的详细信息，请参见 https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/dynamodb.html#DynamoDB.Client.update_item 您将要查看这些选项并看看那里的好例子，了解如何做不同的事情.

Full details of all the options are available at https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/dynamodb.html#DynamoDB.Client.update_item You'll want to review those options and look at the good examples there for how to do different things.

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