Key condition expressions in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a key condition expression in DynamoDB?

A key condition expression specifies the key values to search for in a DynamoDB table or index. It helps DynamoDB find items by matching the partition key and optionally the sort key.

beginner

Which key(s) must be included in a key condition expression?

The partition key must always be included. The sort key can be included optionally with conditions like equals, less than, greater than, or between.

intermediate

Example of a key condition expression to find items with partition key 'User123' and sort key greater than 100.

KeyConditionExpression: "UserId = :userId AND Score > :score" ExpressionAttributeValues: {":userId": {"S": "User123"}, ":score": {"N": "100"}}

intermediate

Can you use non-key attributes in a key condition expression?

No. Key condition expressions only work with the partition key and sort key attributes. Non-key attributes must be filtered using filter expressions after the query.

intermediate

What operators can be used with the sort key in a key condition expression?

You can use =, <, <=, >, >=, BETWEEN, and BEGINS_WITH operators with the sort key in key condition expressions.

Which key is mandatory in a DynamoDB key condition expression?

A Partition key

B Sort key

C Any attribute

D Non-key attribute

The partition key must always be specified in a key condition expression to identify the partition to query.

Can you use a filter expression inside a key condition expression?

A Yes, always

B No, filter expressions are separate

C Only with partition key

D Only with sort key

Filter expressions are applied after the key condition expression to further filter results, but they are separate.

Which operator is NOT valid in a key condition expression for the sort key?

A LIKE

B BEGINS_WITH

C BETWEEN

D >

The LIKE operator is not supported in key condition expressions; use BEGINS_WITH for prefix matching.

What happens if you omit the sort key in a key condition expression on a table with a composite key?

A Query returns no items

B Query fails with error

C Query returns all items with the partition key

D Query returns items with any partition key

If the sort key is omitted, the query returns all items with the specified partition key.

Which of these is a valid key condition expression?

A UserId = :uid AND Age > :age

B Status = :status

C Age > :age

D UserId = :uid AND OrderDate BETWEEN :start AND :end

Only partition key and sort key attributes can be used in key condition expressions. Age and Status are non-key attributes.

Explain what a key condition expression is and why it is important in DynamoDB queries.

Think about how DynamoDB uses keys to find data quickly.

Describe the difference between key condition expressions and filter expressions in DynamoDB.

Consider when each expression is applied during a query.