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One or more substitution tokens for attribute names in an expression. The following are some use cases for using ExpressionAttributeNames:

To access an attribute whose name conflicts with a DynamoDB reserved word.

To create a placeholder for repeating occurrences of an attribute name

in an expression.

To prevent special characters in an attribute name from being misinterpreted

in an expression.

Use the # character in an expression to dereference an attribute name.

For example, consider the following attribute name:


The name of this attribute conflicts with a reserved word, so it cannot

be used directly in an expression. (For the complete list of reserved words, see Reserved Words ( in the Amazon DynamoDB Developer Guide). To work around this, you could specify the following for ExpressionAttributeNames:


You could then use this substitution in an expression, as in this example:

 #P = :val

 Tokens that begin with the : character are expression attribute values,

which are placeholders for the actual value at runtime.

For more information on expression attribute names, see Accessing Item

Attributes ( in the Amazon DynamoDB Developer Guide.

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