Expression attribute names in DynamoDB - Mini Project: Build & Apply

Using Expression Attribute Names in DynamoDB Queries

📖 Scenario: You are managing a DynamoDB table that stores information about books in a library. Some attribute names in the table are reserved words in DynamoDB, so you need to use expression attribute names to query the table safely.

🎯 Goal: Build a DynamoDB query that uses expression attribute names to safely access reserved attribute names in the table.

📋 What You'll Learn

Create a dictionary called expression_attribute_names with the correct mapping for reserved attribute names

Create a string called key_condition_expression using placeholders for attribute names

Write a query dictionary called query_params that includes the table name, key condition expression, and expression attribute names

Complete the query dictionary by adding the ExpressionAttributeNames key with the correct variable

💡 Why This Matters

🌍 Real World

In real-world DynamoDB usage, reserved words can cause errors if used directly in expressions. Expression attribute names let you safely reference these attributes.

💼 Career

Understanding expression attribute names is essential for developers working with DynamoDB to write safe and effective queries and updates.

1

Create the expression attribute names dictionary

Create a dictionary called expression_attribute_names that maps '#yr' to 'year' and '#nm' to 'name'.

DynamoDB

# Create the expression_attribute_names dictionary
# Your code here

Need a hint?

Use a dictionary with keys starting with '#' to map to the actual attribute names.

2

Create the key condition expression string

Create a string variable called key_condition_expression with the value '#yr = :year_val' to use in the query.

DynamoDB

expression_attribute_names = {'#yr': 'year', '#nm': 'name'}
# Create the key_condition_expression string
# Your code here

Need a hint?

Use the placeholder #yr in the string to refer to the reserved attribute year.

3

Create the query parameters dictionary

Create a dictionary called query_params with keys TableName, KeyConditionExpression, and ExpressionAttributeValues. Set TableName to 'Books', KeyConditionExpression to the variable key_condition_expression, and ExpressionAttributeValues to {':year_val': 2020}.

DynamoDB

expression_attribute_names = {'#yr': 'year', '#nm': 'name'}
key_condition_expression = '#yr = :year_val'
# Create the query_params dictionary
# Your code here

Need a hint?

Use the variable key_condition_expression for the key condition expression value.

4

Add ExpressionAttributeNames to the query parameters

Add the key 'ExpressionAttributeNames' to the query_params dictionary and set its value to the variable expression_attribute_names.

DynamoDB

expression_attribute_names = {'#yr': 'year', '#nm': 'name'}
key_condition_expression = '#yr = :year_val'
query_params = {
    'TableName': 'Books',
    'KeyConditionExpression': key_condition_expression,
    'ExpressionAttributeValues': {':year_val': 2020}
}
# Add ExpressionAttributeNames to query_params
# Your code here

Need a hint?

Set the ExpressionAttributeNames key in query_params to the variable expression_attribute_names.