# Update
<a name="API_Update"></a>

Represents a request to perform an `UpdateItem` operation.

## Contents
<a name="API_Update_Contents"></a>

**Note**  
In the following list, the required parameters are described first.

 ** Key **   <a name="DDB-Type-Update-Key"></a>
The primary key of the item to be updated. Each element consists of an attribute name and a value for that attribute.  
Type: String to [AttributeValue](API_AttributeValue.md) object map  
Key Length Constraints: Maximum length of 65535.  
Required: Yes

 ** TableName **   <a name="DDB-Type-Update-TableName"></a>
Name of the table for the `UpdateItem` request. You can also provide the Amazon Resource Name (ARN) of the table in this parameter.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 1024.  
Required: Yes

 ** UpdateExpression **   <a name="DDB-Type-Update-UpdateExpression"></a>
An expression that defines one or more attributes to be updated, the action to be performed on them, and new value(s) for them.  
Type: String  
Required: Yes

 ** ConditionExpression **   <a name="DDB-Type-Update-ConditionExpression"></a>
A condition that must be satisfied in order for a conditional update to succeed.  
Type: String  
Required: No

 ** ExpressionAttributeNames **   <a name="DDB-Type-Update-ExpressionAttributeNames"></a>
One or more substitution tokens for attribute names in an expression.  
Type: String to string map  
Value Length Constraints: Maximum length of 65535.  
Required: No

 ** ExpressionAttributeValues **   <a name="DDB-Type-Update-ExpressionAttributeValues"></a>
One or more values that can be substituted in an expression.  
Type: String to [AttributeValue](API_AttributeValue.md) object map  
Required: No

 ** ReturnValuesOnConditionCheckFailure **   <a name="DDB-Type-Update-ReturnValuesOnConditionCheckFailure"></a>
Use `ReturnValuesOnConditionCheckFailure` to get the item attributes if the `Update` condition fails. For `ReturnValuesOnConditionCheckFailure`, the valid values are: NONE and ALL\$1OLD.  
Type: String  
Valid Values: `ALL_OLD | NONE`   
Required: No

## See Also
<a name="API_Update_SeeAlso"></a>

For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/dynamodb-2012-08-10/Update) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/dynamodb-2012-08-10/Update) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/dynamodb-2012-08-10/Update)