Query with sort key conditions in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to query items with a specific partition key.

DynamoDB

response = table.query(KeyConditionExpression=Key('UserId').eq([1]))

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

A'user123'

Buser123

CUserId

DKey('UserId')

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the partition key value.

Using the key name instead of the key value.

You need to provide the partition key value as a string inside quotes.

2fill in blank

medium

Complete the code to query items where the sort key is greater than a given value.

DynamoDB

response = table.query(KeyConditionExpression=Key('UserId').eq('user123') & Key('Timestamp').[1](1000))

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

Alt

Bgt

Ceq

Dbegins_with

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'lt' which means less than.

Using 'eq' which means equal to.

The sort key condition 'gt' means greater than the given value.

3fill in blank

hard

Fix the error in the code to query items where the sort key begins with a prefix.

DynamoDB

response = table.query(KeyConditionExpression=Key('UserId').eq('user123') & Key('Timestamp').[1]('2023-'))

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

Acontains

Bstartswith

Cbegins_with

Dstarts

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startswith' which is not valid in DynamoDB.

Using 'contains' which checks substring anywhere.

The correct method to check prefix in DynamoDB is 'begins_with'.

4fill in blank

hard

Fill both blanks to query items with partition key 'user123' and sort key less than 5000.

DynamoDB

response = table.query(KeyConditionExpression=Key([1]).eq([2]) & Key('Timestamp').lt(5000))

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

A'UserId'

B'user123'

C'Timestamp'

D'5000'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the sort key name in the first blank.

Not putting quotes around the strings.

The partition key is 'UserId' and its value is 'user123'.

5fill in blank

hard

Fill all three blanks to query items where partition key is 'user123', sort key begins with '2023-', and sort key is greater than 1000.

DynamoDB

response = table.query(KeyConditionExpression=Key([1]).eq([2]) & Key([3]).begins_with('2023-') & Key('Timestamp').gt(1000))

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

A'UserId'

B'user123'

C'Timestamp'

D'Date'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up partition key and sort key names.

Not using quotes around string values.

The partition key is 'UserId' with value 'user123'. The sort key is 'Timestamp' which begins with '2023-' and is greater than 1000.

Practice

1. In DynamoDB, when you use a Query operation with a sort key condition, which of the following is always required?

easy

A. Specify only the sort key condition without the partition key

B. Use a scan operation instead of query

C. Specify the partition key with '=' and a condition on the sort key

D. Specify only the partition key without any sort key condition

Solution

1. Step 1: Understand Query requirements

   A DynamoDB Query must always specify the partition key with '=' to identify the partition.

2. Step 2: Add sort key condition

   You can add conditions on the sort key to filter items within that partition.

3. Final Answer:

   Specify the partition key with '=' and a condition on the sort key -> Option C

4. Quick Check:

   Partition key '=' + sort key condition = required [OK]

Hint: Partition key '=' is mandatory in Query with sort key condition [OK]

Common Mistakes:

• Trying to query without specifying partition key
• Using scan instead of query for sort key filtering
• Specifying only sort key condition without partition key

2. Which of the following is the correct syntax for a DynamoDB Query with a sort key condition to find items where the sort key Timestamp is greater than 1000?

easy

A. KeyConditionExpression: 'PartitionKey > :pk AND Timestamp > :ts', ExpressionAttributeValues: { ':pk': 'User1', ':ts': 1000 }

B. KeyConditionExpression: 'PartitionKey = :pk OR Timestamp > :ts', ExpressionAttributeValues: { ':pk': 'User1', ':ts': 1000 }

C. KeyConditionExpression: 'PartitionKey = :pk AND Timestamp == :ts', ExpressionAttributeValues: { ':pk': 'User1', ':ts': 1000 }

D. KeyConditionExpression: 'PartitionKey = :pk AND Timestamp > :ts', ExpressionAttributeValues: { ':pk': 'User1', ':ts': 1000 }

Solution

1. Step 1: Use '=' for partition key

   The partition key must be compared with '=' in the KeyConditionExpression.

2. Step 2: Use '>' for sort key condition

   The sort key condition can use operators like '>' to filter items.

3. Final Answer:

   KeyConditionExpression: 'PartitionKey = :pk AND Timestamp > :ts' -> Option D

4. Quick Check:

   PartitionKey '=' and sort key '>' correct syntax [OK]

Hint: Partition key '=' and sort key condition combined with AND [OK]

Common Mistakes:

• Using OR instead of AND in KeyConditionExpression
• Using '>' for partition key instead of '='
• Using '==' instead of '=' for partition key

3. Given a DynamoDB table with partition key UserID and sort key OrderDate, what will the following query return?

KeyConditionExpression: 'UserID = :uid AND OrderDate BETWEEN :start AND :end'
ExpressionAttributeValues: { ':uid': 'user123', ':start': '2023-01-01', ':end': '2023-01-31' }

medium

A. All orders for 'user123' placed between January 1 and January 31, 2023 inclusive

B. All orders for all users placed between January 1 and January 31, 2023

C. All orders for 'user123' placed before January 1, 2023

D. Syntax error due to BETWEEN usage in KeyConditionExpression

Solution

1. Step 1: Partition key '=' filters user

   The query filters items where UserID equals 'user123'.

2. Step 2: Sort key BETWEEN filters date range

   The BETWEEN operator selects OrderDate values from '2023-01-01' to '2023-01-31' inclusive.

3. Final Answer:

   All orders for 'user123' placed between January 1 and January 31, 2023 inclusive -> Option A

4. Quick Check:

   Partition key '=' + sort key BETWEEN returns filtered range [OK]

Hint: BETWEEN filters sort key range within one partition [OK]

Common Mistakes:

• Assuming query returns all users' orders
• Thinking BETWEEN excludes boundary dates
• Believing BETWEEN is invalid in KeyConditionExpression

4. You wrote this DynamoDB query but it returns no results:

KeyConditionExpression: 'UserID = :uid AND OrderDate > :date'
ExpressionAttributeValues: { ':uid': 'user123', ':date': '2023-12-31' }

What is the most likely reason?

medium

A. No items exist with OrderDate after 2023-12-31 for user123

B. Using '>' operator is not allowed in KeyConditionExpression

C. Partition key UserID should use '>' instead of '='

D. ExpressionAttributeValues keys must not start with ':'

Solution

1. Step 1: Check operator validity

   The '>' operator is valid for sort key conditions in DynamoDB queries.

2. Step 2: Consider data existence

   If no items have OrderDate after '2023-12-31' for 'user123', query returns empty.

3. Final Answer:

   No items exist with OrderDate after 2023-12-31 for user123 -> Option A

4. Quick Check:

   Valid syntax but no matching data = empty result [OK]

Hint: Empty results often mean no matching data, not syntax error [OK]

Common Mistakes:

• Thinking '>' is invalid in KeyConditionExpression
• Using '>' for partition key instead of '='
• Misunderstanding ExpressionAttributeValues syntax

5. You want to query a DynamoDB table with partition key CustomerID and sort key InvoiceDate. You need to find all invoices for CustomerID = 'C123' where InvoiceDate is either before '2023-01-01' or after '2023-12-31'. Which approach correctly achieves this?

hard

A. Use KeyConditionExpression with BETWEEN operator for the two date ranges

B. Run two separate queries: one with InvoiceDate < '2023-01-01' and another with InvoiceDate > '2023-12-31', then combine results

C. Use a scan operation with filter expression for the date conditions

D. Use a single query with KeyConditionExpression: CustomerID = :cid AND InvoiceDate < '2023-01-01' OR InvoiceDate > '2023-12-31'

Solution

1. Step 1: Understand KeyConditionExpression limits

   DynamoDB KeyConditionExpression supports only AND between partition key and sort key conditions, no OR.

2. Step 2: Query with OR on sort key requires multiple queries

   To get items before '2023-01-01' OR after '2023-12-31', run two queries and merge results.

3. Final Answer:

   Run two separate queries: one with InvoiceDate < '2023-01-01' and another with InvoiceDate > '2023-12-31', then combine results -> Option B

4. Quick Check:

   OR on sort key = multiple queries combined [OK]

Hint: DynamoDB Query KeyConditionExpression uses AND only; split OR into queries [OK]

Common Mistakes:

• Trying to use OR in KeyConditionExpression
• Using BETWEEN for non-continuous ranges
• Using scan instead of efficient queries