PutItem (creating items) in DynamoDB - Mini Project: Build & Apply

Create and Add Items to a DynamoDB Table

📖 Scenario: You are managing a small online bookstore. You want to store information about books in a DynamoDB table. Each book has a unique BookID, a Title, and an Author.

🎯 Goal: Build a DynamoDB PutItem request step-by-step to add a new book item with exact attributes to the table.

📋 What You'll Learn

Create a dictionary called book_item with keys BookID, Title, and Author and their exact string values.

Create a variable called table_name and set it to the exact string Books.

Create a dictionary called put_request that uses book_item as the Item value.

Create a dictionary called params with the key TableName set to table_name and the key Item set to book_item.

💡 Why This Matters

🌍 Real World

Adding items to a DynamoDB table is a common task when storing data for web applications, such as product catalogs or user profiles.

💼 Career

Understanding how to structure PutItem requests is essential for backend developers working with AWS DynamoDB to manage data storage.

1

Create the book item dictionary

Create a dictionary called book_item with these exact key-value pairs: 'BookID': {'S': 'B001'}, 'Title': {'S': 'The Great Gatsby'}, and 'Author': {'S': 'F. Scott Fitzgerald'}.

DynamoDB

# Create the book_item dictionary with exact keys and values
# Your code here

Hint

Remember, DynamoDB expects attribute values as dictionaries with the type as key, like {'S': 'string value'}.

2

Set the table name

Create a variable called table_name and set it to the string 'Books'.

DynamoDB

book_item = {
    'BookID': {'S': 'B001'},
    'Title': {'S': 'The Great Gatsby'},
    'Author': {'S': 'F. Scott Fitzgerald'}
}
# Create the table_name variable with value 'Books'
# Your code here

Hint

Use a simple string assignment for the table name.

3

Create the PutItem request dictionary

Create a dictionary called put_request with a single key Item set to the book_item dictionary.

DynamoDB

book_item = {
    'BookID': {'S': 'B001'},
    'Title': {'S': 'The Great Gatsby'},
    'Author': {'S': 'F. Scott Fitzgerald'}
}
table_name = 'Books'
# Create put_request dictionary with key 'Item' set to book_item
# Your code here

Hint

The put_request dictionary should have exactly one key: Item.

4

Create the final parameters dictionary

Create a dictionary called params with keys 'TableName' set to table_name and 'Item' set to book_item.

DynamoDB

book_item = {
    'BookID': {'S': 'B001'},
    'Title': {'S': 'The Great Gatsby'},
    'Author': {'S': 'F. Scott Fitzgerald'}
}
table_name = 'Books'
put_request = {'Item': book_item}
# Create params dictionary with keys 'TableName' and 'Item'
# Your code here

Hint

This dictionary is what you would pass to the DynamoDB client to add the item.

Practice

1. What does the PutItem operation do in DynamoDB?

easy

A. Reads an item from a table

B. Deletes an item from a table

C. Updates only specific attributes of an item

D. Adds a new item or replaces an existing item in a table

Solution

1. Step 1: Understand the purpose of PutItem

   PutItem is used to add a new item or replace an existing item in a DynamoDB table.

2. Step 2: Compare with other operations

   Delete removes items, Get reads items, and Update modifies specific attributes, so they differ from PutItem.

3. Final Answer:

   Adds a new item or replaces an existing item in a table -> Option D

4. Quick Check:

   PutItem = Add or replace item [OK]

Hint: PutItem adds or replaces whole items, not partial updates [OK]

Common Mistakes:

• Confusing PutItem with UpdateItem
• Thinking PutItem only adds without replacing
• Mixing PutItem with Delete or Get operations

2. Which of the following is the correct syntax snippet to add an item with PutItem in DynamoDB using AWS SDK?

easy

A. dynamodb.putItem({ TableName: 'Users', Item: { 'UserId': { S: '123' }, 'Name': { S: 'Alice' } } })

B. dynamodb.put({ Table: 'Users', Item: { UserId: '123', Name: 'Alice' } })

C. dynamodb.insertItem({ TableName: 'Users', Item: { 'UserId': '123', 'Name': 'Alice' } })

D. dynamodb.addItem({ TableName: 'Users', Item: { 'UserId': { N: 123 }, 'Name': { S: 'Alice' } } })

Solution

1. Step 1: Check the correct method and parameters

   The AWS SDK method is putItem with parameters TableName and Item where each attribute has a type like S for string.

2. Step 2: Validate the attribute format

   dynamodb.putItem({ TableName: 'Users', Item: { 'UserId': { S: '123' }, 'Name': { S: 'Alice' } } }) uses the correct method and attribute typing. Other options use wrong method names or omit types.

3. Final Answer:

   dynamodb.putItem({ TableName: 'Users', Item: { 'UserId': { S: '123' }, 'Name': { S: 'Alice' } } }) -> Option A

4. Quick Check:

   Correct method and typed attributes = dynamodb.putItem({ TableName: 'Users', Item: { 'UserId': { S: '123' }, 'Name': { S: 'Alice' } } }) [OK]

Hint: Use putItem with typed attributes like { S: 'value' } [OK]

Common Mistakes:

• Using wrong method names like put or insertItem
• Not specifying attribute types (S, N, etc.)
• Using wrong parameter names like Table instead of TableName

3. Given the following PutItem request, what will be the result in the DynamoDB table?

{
  TableName: 'Products',
  Item: {
    'ProductId': { S: 'p100' },
    'Name': { S: 'Pen' },
    'Price': { N: '5' }
  }
}

medium

A. An error occurs because Price is a number but given as a string

B. Only the ProductId attribute is saved, others are ignored

C. A new item with ProductId 'p100', Name 'Pen', and Price 5 is added or replaced

D. The item is added but Price is stored as a string, not number

Solution

1. Step 1: Understand attribute types in PutItem

   In DynamoDB, number attributes are passed as strings inside the N type, so '5' is valid for number.

2. Step 2: Result of PutItem operation

   The item with all specified attributes is added or replaces existing item with same ProductId.

3. Final Answer:

   A new item with ProductId 'p100', Name 'Pen', and Price 5 is added or replaced -> Option C

4. Quick Check:

   PutItem stores typed attributes correctly = A new item with ProductId 'p100', Name 'Pen', and Price 5 is added or replaced [OK]

Hint: Number values are strings inside N type in PutItem [OK]

Common Mistakes:

• Thinking number values must be numeric type, not string
• Assuming partial attributes are saved
• Confusing attribute types and values

4. You try to run this PutItem request but get an error:

{
  TableName: 'Orders',
  Item: {
    'OrderId': 'o123',
    'Amount': { N: '100' }
  }
}

What is the likely cause of the error?

medium

A. The table name 'Orders' is invalid

B. The attribute 'OrderId' is missing its type wrapper like { S: 'o123' }

C. The number value '100' should be a number, not a string

D. The Item object must be an array, not an object

Solution

1. Step 1: Check attribute format in Item

   Each attribute must specify its type, e.g., { S: 'value' } for strings. Here, 'OrderId' lacks the type wrapper.

2. Step 2: Validate other parts

   TableName is valid, number values are strings inside N, and Item is an object, so those are correct.

3. Final Answer:

   The attribute 'OrderId' is missing its type wrapper like { S: 'o123' } -> Option B

4. Quick Check:

   All attributes need type wrappers = The attribute 'OrderId' is missing its type wrapper like { S: 'o123' } [OK]

Hint: Always wrap attributes with type like { S: 'text' } or { N: '123' } [OK]

Common Mistakes:

• Omitting type wrappers for string attributes
• Confusing number values as numeric instead of string
• Assuming Item can be an array

5. You want to add a new user item with UserId as the primary key and optional Age attribute only if it is provided (not null). Which PutItem approach correctly handles this conditional attribute?

hard

A. Include Age in the Item only if it is not null, otherwise omit it

B. Always include Age with value { N: '0' } if null

C. Set Age to an empty string { S: '' } when null

D. Use PutItem with a condition expression to skip Age attribute

Solution

1. Step 1: Understand optional attribute handling

   In DynamoDB PutItem, you include only attributes you want saved. Omitting optional attributes if null is correct.

2. Step 2: Evaluate other options

   Setting Age to zero or empty string changes data meaning. Condition expressions control item existence, not attribute presence.

3. Final Answer:

   Include Age in the Item only if it is not null, otherwise omit it -> Option A

4. Quick Check:

   Omit null attributes to avoid wrong data = Include Age in the Item only if it is not null, otherwise omit it [OK]

Hint: Only add attributes if they have real values, omit nulls [OK]

Common Mistakes:

• Adding attributes with zero or empty string instead of omitting
• Misusing condition expressions for attribute presence
• Assuming PutItem auto-skips null attributes