Hierarchical data modeling in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the partition key for a DynamoDB table storing hierarchical data.

DynamoDB

KeySchema: [{ AttributeName: [1], KeyType: 'HASH' }]

Drag options to blanks, or click blank then click option'

AParentId

BItemId

CSortKey

DCategory

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ItemId' as partition key prevents efficient retrieval of all children under a parent.

The partition key 'ParentId' groups all child items under the same parent for efficient hierarchical queries.

2fill in blank

medium

Complete the code to define the sort key for ordering child items under a parent in DynamoDB.

DynamoDB

KeySchema: [{ AttributeName: 'ParentId', KeyType: 'HASH' }, { AttributeName: [1], KeyType: 'RANGE' }]

Drag options to blanks, or click blank then click option'

AParentId

BCategory

CTimestamp

DChildId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ParentId' as sort key, which duplicates the partition key.

The sort key 'ChildId' uniquely identifies and allows ordering of child items under the same parent.

3fill in blank

hard

Fix the error in the DynamoDB query to fetch all children of a parent item.

DynamoDB

const params = { TableName: 'Items', KeyConditionExpression: '[1] = :parentId', ExpressionAttributeValues: { ':parentId': 'parent456' } };

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AChildId

BCategory

CParentId

DSortKey

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a sort key condition like 'ChildId = :id', which returns only one child.

The KeyConditionExpression uses only the partition key 'ParentId = :parentId' to retrieve all children under the parent.

4fill in blank

hard

Fill both blanks to create a DynamoDB item representing a child with a reference to its parent.

DynamoDB

Item: { 'ChildId': [1], 'ParentId': [2], 'Name': 'Child Item' }

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A'child123'

B'parent456'

C'child456'

D'parent123'

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping child and parent IDs.

The 'ChildId' is the child's unique ID (sort key), and 'ParentId' references the parent's ID (partition key).

5fill in blank

hard

Fill all three blanks to write a DynamoDB query that retrieves all children of a parent sorted by child ID.

DynamoDB

const params = { TableName: 'Items', KeyConditionExpression: '[1] = :parentId', ExpressionAttributeValues: { ':parentId': [2] }, ScanIndexForward: [3] };

Drag options to blanks, or click blank then click option'

AParentId

B'parent456'

Ctrue

DItemId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ItemId' instead of 'ParentId' in the condition.

Using false for ScanIndexForward when ascending order is needed.

The query filters by 'ParentId' equal to the parent's ID and sorts results in ascending order by ChildId (ScanIndexForward: true).