Expression attribute names in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are Expression Attribute Names in DynamoDB?

Expression Attribute Names are placeholders used in DynamoDB queries to substitute attribute names that are reserved words or contain special characters.

beginner

Why do we use Expression Attribute Names in DynamoDB queries?

We use Expression Attribute Names to avoid conflicts with reserved keywords and to safely reference attribute names that contain special characters or spaces.

intermediate

How do you define an Expression Attribute Name in a DynamoDB query?

You define Expression Attribute Names by using a map with keys starting with '#' and values as the actual attribute names, for example: {"#yr": "year"}.

intermediate

Example: How to use Expression Attribute Names to query an attribute named 'and' which is a reserved word?

Use a placeholder like '#and' in your expression and map it to 'and' in ExpressionAttributeNames. For example: ExpressionAttributeNames: {"#and": "and"}, KeyConditionExpression: "#and = :value".

intermediate

Can Expression Attribute Names be used with Update Expressions in DynamoDB?

Yes, Expression Attribute Names can be used in Update Expressions to safely reference attribute names that might conflict with reserved words or contain special characters.

What symbol must Expression Attribute Names start with in DynamoDB?

A @

B :

C #

D $

Expression Attribute Names always start with '#' to distinguish them from other placeholders.

Why might you need to use Expression Attribute Names in a DynamoDB query?

A To encrypt data

B To speed up queries

C To change data types

D To avoid reserved word conflicts

Expression Attribute Names help avoid conflicts with reserved words or special characters in attribute names.

Which of the following is a correct way to define an Expression Attribute Name for the attribute 'status'?

A {"st": "#status"}

B {"#st": "status"}

C {"#status": ":st"}

D {"status": "#st"}

The key must start with '#' and the value is the actual attribute name.

Can Expression Attribute Names be used in Filter Expressions?

A Yes

B No

C Only in KeyConditionExpression

D Only in ProjectionExpression

Expression Attribute Names can be used in any expression including FilterExpression to avoid reserved word conflicts.

If an attribute name contains a space, how should you reference it in a DynamoDB expression?

A Use an Expression Attribute Name placeholder starting with '#'

B Use the attribute name directly

C Replace spaces with underscores

D Use quotes around the attribute name

Attribute names with spaces must be replaced with Expression Attribute Names starting with '#' to be valid.

Explain what Expression Attribute Names are and why they are important in DynamoDB queries.

Think about how DynamoDB handles reserved words and special characters.

Describe how to use Expression Attribute Names in a DynamoDB Update Expression with an example.

Use '#' placeholders and show how to update an attribute safely.