ADD expression for numeric increment in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the ADD expression do in DynamoDB?

The ADD expression increases (or decreases) the value of a numeric attribute by a specified amount. It can also add elements to a set attribute.

beginner

How do you increment a numeric attribute named 'counter' by 1 using the ADD expression?

Use the UpdateExpression: <br>ADD counter :inc<br>where :inc is a value of 1 in ExpressionAttributeValues.

intermediate

Can the ADD expression be used to decrement a numeric attribute in DynamoDB?

Yes, by adding a negative number. For example, ADD counter :dec where :dec is -1 will decrement the counter by 1.

intermediate

What happens if the attribute does not exist when you use ADD to increment it?

DynamoDB creates the attribute and sets it to the increment value. For example, if 'counter' does not exist and you ADD 1, 'counter' becomes 1.

advanced

Is the ADD expression atomic in DynamoDB updates?

Yes, the ADD operation is atomic, meaning it safely increments or decrements the attribute even if multiple updates happen at the same time.

Which DynamoDB UpdateExpression syntax increments a numeric attribute 'score' by 5?

A ADD score :val

B SET score = score + 5

C ADD score 5

D SET score + 5

The correct syntax uses ADD with a placeholder value, e.g., ADD score :val where :val is 5.

What value should you provide to decrement a numeric attribute by 3 using ADD?

A 0

B 3

C -3

D Cannot decrement with ADD

You provide a negative number, so -3 will decrement the attribute by 3.

If the attribute 'visits' does not exist, what will ADD visits :inc with :inc = 1 do?

A Create 'visits' with value 1

B Return an error

C Ignore the update

D Set 'visits' to 0

DynamoDB creates the attribute and sets it to the increment value.

Is the ADD operation in DynamoDB atomic?

A Only when used with SET

B No, it can cause conflicts

C Only for string attributes

D Yes, it prevents race conditions

ADD is atomic, so concurrent updates safely increment or decrement the attribute.

Which data types can the ADD expression modify in DynamoDB?

A Only numeric attributes

B Numeric attributes and sets

C Only string attributes

D All attribute types

ADD can increment numeric attributes and add elements to set attributes.

Explain how the ADD expression works for incrementing a numeric attribute in DynamoDB.

Think about how you tell DynamoDB to add a number to an attribute safely.

Describe how you would decrement a numeric attribute using the ADD expression in DynamoDB.

Remember ADD can add negative values to subtract.