如何在DynamoDB中查询一列的所有行？

Question

I just work with AWS DynamoDB in a short of time. I am wondering how can I get the same result with this statement (without WHERE clause):

SELECT column1 FROM DynamoTable;

I tried (but failed) with:

 import boto3
 dynamodb = boto3.resource('dynamodb')
 table = dynamodb.Table('DynamoTable')
 from boto3.dynamodb.conditions import Key, Attr
 resp = table.query(KeyConditionExpression=Key('column1'))

It requires Key().eq() or Key().begin_with() ...

I tried with resp = table.scan() already, but the response data is too many fields while I only need column1

Thanks.

Answer 1

You should definitely use Scan operation . Check the documentation to implement it with python.

Regarding how to select just a specific attribute you could use:

import boto3

def getColumn1Items():
    dynamodb = boto3.resource('dynamodb')
    table = dynamodb.Table('DynamoTable')
    response = table.scan()

    lst = []
    for i in response['Items']:
        lst.append(i['column1'])

    return lst

You have to iterate over the the entire table and just fetch the column you need.

Answer 2

This lets you get the required column directly and you do not need to iterate over the whole dataset

import boto3

def getColumn1Items():
     dynamodb = boto3.resource('dynamodb')
     table = dynamodb.Table('DynamoTable')
     resp = table.scan(AttributesToGet=['column1'])

     return resp['Items']