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Merge Entity

Updated: February 10, 2014

The Merge Entity operation updates an existing entity by updating the entity's properties. This operation does not replace the existing entity, as the Update Entity operation does.

The Merge Entity request may be constructed as follows. HTTPS is recommended. Replace myaccount with the name of your storage account, mytable with the name of your table, and myPartitionKey and myRowKey with the name of the partition key and row key identifying the entity to be updated:

 

Method Request URI HTTP Version

MERGE

https://myaccount.table.core.windows.net/mytable(PartitionKey='myPartitionKey', RowKey='myRowKey')

HTTP/1.1

The address of the entity to be updated may take a number of forms on the request URI. See the OData URI Conventions for additional details.

When making a request against the emulated storage service, specify the emulator hostname and Table service port as 127.0.0.1:10002, followed by the emulated storage account name:

 

Method Request URI HTTP Version

MERGE

http://127.0.0.1:10002/devstoreaccount1/mytable(PartitionKey='myPartitionKey', RowKey='myRowKey')

HTTP/1.1

The Table service in the storage emulator differs from the Windows® Azure™ Table service in several ways. For more information, see About Development Storage and Differences Between the Storage Emulator and Azure Storage Services.

The following table describes required and optional request headers.

 

Request header Description

Authorization

Required. Specifies the authentication scheme, account name, and signature. For more information, see Authentication for the Azure Storage Services.

Date or x-ms-date

Required. Specifies the Coordinated Universal Time (UTC) for the request. For more information, see Authentication for the Azure Storage Services.

x-ms-version

Optional. Specifies the version of the operation to use for this request. For more information, see Versioning for the Azure Storage Services.

Content-Type

Required. Specifies the content type of the payload. Possible values are application/atom+xml and application/json.

For more information about valid content types, see Payload Format for Table Service Operations.

Content-Length

Required. The length of the request body.

If-Match

Required. The client may specify the ETag for the entity on the request in order to compare to the ETag maintained by the service for the purpose of optimistic concurrency. The update operation will be performed only if the ETag sent by the client matches the value maintained by the server, indicating that the entity has not been modified since it was retrieved by the client.

To force an unconditional update, set If-Match to the wildcard character (*).

x-ms-client-request-id

Optional. Provides a client-generated, opaque value with a 1 KB character limit that is recorded in the analytics logs when storage analytics logging is enabled. Using this header is highly recommended for correlating client-side activities with requests received by the server. For more information, see About Storage Analytics Logging and Windows Azure Logging: Using Logs to Track Storage Requests.

The Merge Entity operation sends the entity to be updated as an OData entity, which may be either a JSON or an Atom feed. For more information, see Inserting and Updating Entities.

The response includes an HTTP status code and a set of response headers.

A successful operation returns status code 204 (No Content).

For information about status codes, see Status and Error Codes and Table Service Error Codes.

The response for this operation includes the following headers. The response may also include additional standard HTTP headers. All standard headers conform to the HTTP/1.1 protocol specification.

 

Response header Description

ETag

The ETag for the entity.

x-ms-request-id

This header uniquely identifies the request that was made and can be used for troubleshooting the request. For more information, see Troubleshooting API Operations.

x-ms-version

Indicates the version of the Table service used to execute the request. This header is returned for requests made against version 2009-09-19 and later.

Date

A UTC date/time value generated by the service that indicates the time at which the response was initiated.

Response Status:
HTTP/1.1 204 No Content

Response Headers:
Connection: Keep-Alive
Content-Length: 0
Cache-Control: no-cache
Date: Mon, 25 Nov 2013 19:06:47 GMT
ETag: W/"0x5B168C7B6E589D2"
x-ms-version: 2013-08-15
DataServiceVersion: 1.0;NetFx
MaxDataServiceVersion: 2.0;NetFx
Server: Windows-Azure-Table/1.0 Microsoft-HTTPAPI/2.0

This operation can be performed by the account owner and by anyone with a shared access signature that has permission to perform this operation.

Any properties with null values are ignored by the Merge Entity operation. All other properties will be updated.

A property cannot be removed with a Merge Entity operation. To remove a property from an entity, replace the entity by calling the Update Entity operation.

When merging an entity, you must specify the PartitionKey and RowKey system properties as part of the merge operation.

An entity's ETag provides default optimistic concurrency for merge operations. The ETag value is opaque and should not be read or relied upon. Before a merge operation occurs, the Table service verifies that the entity's current ETag value is identical to the ETag value included with the request in the If-Match header. If the values are identical, the Table service determines that the entity has not been modified since it was retrieved, and the merge operation proceeds.

If the entity's ETag differs from that specified with the merge request, the merge operation fails with status code 412 (Precondition Failed). This error indicates that the entity has been changed on the server since it was retrieved. To resolve this error, retrieve the entity again and reissue the request.

To force an unconditional merge operation, set the value of the If-Match header to the wildcard character (*) on the request. Passing this value to the operation will override the default optimistic concurrency and ignore any mismatch in ETag values.

If the If-Match header is missing from the request, the service returns status code 400 (Bad Request). A request malformed in other ways may also return 400; for more information, see Table Service Error Codes.

Any application that can authenticate and send an HTTP MERGE request can merge an entity. For more information about constructing a query by using HTTP MERGE, see How to: Add, Modify, and Delete Entities.

For information about performing batch merge operations, see Performing Entity Group Transactions.

See Also

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