Query with sort key conditions in DynamoDB - Mini Project: Build & Apply

Query with sort key conditions in DynamoDB

📖 Scenario: You are managing a DynamoDB table that stores orders for an online store. Each order has a customer_id as the partition key and an order_date as the sort key. You want to find all orders for a specific customer within a certain date range.

🎯 Goal: Build a DynamoDB query that retrieves all orders for customer_id 'C123' where the order_date is between '2023-01-01' and '2023-01-31'.

📋 What You'll Learn

Create a variable called key_condition_expression that specifies the partition key equals 'C123' and the sort key is between '2023-01-01' and '2023-01-31' using DynamoDB condition functions.

Create a dictionary called expression_attribute_values with the exact keys :cust_id, :start_date, and :end_date and their corresponding values.

Write a query call using table.query() with the parameters KeyConditionExpression and ExpressionAttributeValues using the variables above.

Add a ScanIndexForward=False parameter to the query to sort results in descending order by order_date.

💡 Why This Matters

🌍 Real World

Querying DynamoDB tables with partition and sort key conditions is common in real-world applications like e-commerce order tracking, where you want to find all orders for a customer within a date range.

💼 Career

Understanding how to write DynamoDB queries with key conditions and sorting is essential for backend developers and cloud engineers working with AWS databases.

1

Create the key condition expression dictionary

Create a variable called key_condition_expression that uses the DynamoDB condition functions to specify customer_id equals :cust_id and order_date is between :start_date and :end_date. Use Key('customer_id').eq(:cust_id) & Key('order_date').between(:start_date, :end_date) exactly.

DynamoDB

# Your code here

Need a hint?

Use Key from boto3.dynamodb.conditions to build the condition.

2

Create the expression attribute values dictionary

Create a dictionary called expression_attribute_values with keys ':cust_id', ':start_date', and ':end_date' and values 'C123', '2023-01-01', and '2023-01-31' respectively.

DynamoDB

from boto3.dynamodb.conditions import Key

key_condition_expression = Key('customer_id').eq(:cust_id) & Key('order_date').between(:start_date, :end_date)

# Your code here

Need a hint?

Use a dictionary with the exact keys and values as shown.

3

Write the DynamoDB query call

Write a query call using table.query() with parameters KeyConditionExpression=key_condition_expression and ExpressionAttributeValues=expression_attribute_values. Assign the result to a variable called response.

DynamoDB

from boto3.dynamodb.conditions import Key

key_condition_expression = Key('customer_id').eq(:cust_id) & Key('order_date').between(:start_date, :end_date)

expression_attribute_values = {
    ':cust_id': 'C123',
    ':start_date': '2023-01-01',
    ':end_date': '2023-01-31'
}

# Your code here

Need a hint?

Use table.query() with the correct parameters.

4

Add descending sort order to the query

Add the parameter ScanIndexForward=False to the table.query() call to sort the results by order_date in descending order.

DynamoDB

from boto3.dynamodb.conditions import Key

key_condition_expression = Key('customer_id').eq(:cust_id) & Key('order_date').between(:start_date, :end_date)

expression_attribute_values = {
    ':cust_id': 'C123',
    ':start_date': '2023-01-01',
    ':end_date': '2023-01-31'
}

response = table.query(
    KeyConditionExpression=key_condition_expression,
    ExpressionAttributeValues=expression_attribute_values,
    # Your code here
)

Need a hint?

Set ScanIndexForward to False inside the query call.