Query result ordering (ascending, descending) in DynamoDB - Mini Project: Build & Apply

Query result ordering (ascending, descending)

📖 Scenario: You are managing a small online bookstore database using DynamoDB. You want to retrieve books sorted by their publication year, either from oldest to newest or newest to oldest.

🎯 Goal: Build a DynamoDB query that fetches books ordered by their publication_year in ascending or descending order.

📋 What You'll Learn

Create a DynamoDB table named Books with author as the partition key and publication_year as the sort key.

Set a variable author_name to query books by a specific author.

Write a query to get books by author_name ordered by publication_year ascending.

Modify the query to order the results by publication_year descending.

💡 Why This Matters

🌍 Real World

Ordering query results is common when you want to show data sorted by dates, prices, or other criteria in apps like bookstores, blogs, or event listings.

💼 Career

Understanding how to order query results in DynamoDB is important for backend developers and database administrators working with AWS services.

1

Create the DynamoDB table structure

Create a DynamoDB table named Books with author as the partition key and publication_year as the sort key.

DynamoDB

# Define the Books table with author as partition key and publication_year as sort key
# Your code here

Need a hint?

Use KeySchema to define partition and sort keys. author is HASH key, publication_year is RANGE key.

2

Set the author name to query

Create a variable called author_name and set it to the string 'J.K. Rowling' to specify the author for the query.

DynamoDB

Books = {
    'TableName': 'Books',
    'KeySchema': [
        {'AttributeName': 'author', 'KeyType': 'HASH'},
        {'AttributeName': 'publication_year', 'KeyType': 'RANGE'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'author', 'AttributeType': 'S'},
        {'AttributeName': 'publication_year', 'AttributeType': 'N'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}

# Set the author_name variable to 'J.K. Rowling'
# Your code here

Need a hint?

Assign the exact string 'J.K. Rowling' to the variable author_name.

3

Write a query to get books ordered ascending by publication year

Write a DynamoDB query named query_ascending that queries the Books table for items where author equals author_name, and orders the results by publication_year in ascending order (oldest first). Use KeyConditionExpression and set ScanIndexForward to True.

DynamoDB

Books = {
    'TableName': 'Books',
    'KeySchema': [
        {'AttributeName': 'author', 'KeyType': 'HASH'},
        {'AttributeName': 'publication_year', 'KeyType': 'RANGE'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'author', 'AttributeType': 'S'},
        {'AttributeName': 'publication_year', 'AttributeType': 'N'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}

author_name = 'J.K. Rowling'

# Write query_ascending to get books by author_name ordered by publication_year ascending
# Your code here

Need a hint?

Use ScanIndexForward: True to order ascending by the sort key.

4

Modify the query to order descending by publication year

Create a new query named query_descending that is the same as query_ascending but orders the results by publication_year in descending order (newest first). Set ScanIndexForward to False.

DynamoDB

Books = {
    'TableName': 'Books',
    'KeySchema': [
        {'AttributeName': 'author', 'KeyType': 'HASH'},
        {'AttributeName': 'publication_year', 'KeyType': 'RANGE'}
    ],
    'AttributeDefinitions': [
        {'AttributeName': 'author', 'AttributeType': 'S'},
        {'AttributeName': 'publication_year', 'AttributeType': 'N'}
    ],
    'ProvisionedThroughput': {
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5
    }
}

author_name = 'J.K. Rowling'

query_ascending = {
    'TableName': 'Books',
    'KeyConditionExpression': 'author = :author_val',
    'ExpressionAttributeValues': {':author_val': {'S': author_name}},
    'ScanIndexForward': True
}

# Create query_descending like query_ascending but with ScanIndexForward set to False
# Your code here

Need a hint?

Set ScanIndexForward to False to order descending by the sort key.