ALTER EXTERNAL DATA SOURCE (Transact-SQL)

Статия
01/13/2023

Applies to: SQL Server 2016 (13.x) and later Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Modifies an external data source used to create an external table. The external data source can be Hadoop or Azure Blob Storage (WASBS) for SQL SERVER and Azure Blob Storage (WASBS) or Azure Data Lake storage (ABFSS/ADL) for Azure Synapse Analytics.

Starting in SQL Server 2022 (16.x), Hadoop external data sources are no longer supported. Also, Azure Blob Storage and Azure Data Lake Gen 2 prefixes changed, refer to the following table:

External Data Source	From	To
Azure Blob Storage	wasb[s]	abs
ADLS Gen2	abfs[s]	adls

Syntax

-- Modify an external data source
-- Applies to: SQL Server (2016, 2017 and 2019) and APS
ALTER EXTERNAL DATA SOURCE data_source_name SET
    {   
        LOCATION = '<prefix>://<path>[:<port>]' [,] |
        RESOURCE_MANAGER_LOCATION = <'IP address;Port'> [,] |
        CREDENTIAL = credential_name
    }  
    [;]  

-- Modify an external data source pointing to Azure Blob storage
-- Applies to: SQL Server (2017 and 2019)
ALTER EXTERNAL DATA SOURCE data_source_name
    SET
        LOCATION = 'https://storage_account_name.blob.core.windows.net'
        [, CREDENTIAL = credential_name ] 

-- Modify an external data source pointing to Azure Blob storage
-- Applies to: SQL Server 2022
ALTER EXTERNAL DATA SOURCE data_source_name
    SET
        LOCATION = 'abs://storage_account_name.blob.core.windows.net'
        [, CREDENTIAL = credential_name ] 

-- Modify an external data source pointing to Azure Data Lake Storage Gen2
-- Applies to: SQL Server 2022
ALTER EXTERNAL DATA SOURCE data_source_name
    SET
        LOCATION = 'adls://storage_account_name.dfs.core.windows.net'
        [, CREDENTIAL = credential_name ] 

-- Modify an external data source pointing to Azure Blob storage or Azure Data Lake storage
-- Applies to: Azure Synapse Analytics dedicated SQL pool only
ALTER EXTERNAL DATA SOURCE data_source_name
    SET
        [LOCATION = '<location prefix>://<location path>']
        [, CREDENTIAL = credential_name ]

Arguments

data_source_name Specifies the user-defined name for the data source. The name must be unique.

LOCATION = '<prefix>://<path>[:<port>]' Provides the connectivity protocol, path, and port to the external data source. See CREATE EXTERNAL DATA SOURCE (Transact-SQL) for valid location options.

RESOURCE_MANAGER_LOCATION = '<IP address;Port>' (Doesn't apply to Azure Synapse Analytics and SQL Server 2022 (16.x)) Specifies the Hadoop Resource Manager location. When specified, the query optimizer might choose to pre-process data for a PolyBase query by using Hadoop's computation capabilities. This is a cost-based decision. Called predicate pushdown, this can significantly reduce the volume of data transferred between Hadoop and SQL, and therefore improve query performance.

CREDENTIAL = Credential_Name Specifies the named credential. See CREATE DATABASE SCOPED CREDENTIAL (Transact-SQL).

TYPE = [HADOOP | BLOB_STORAGE] Applies to: SQL Server 2017 (14.x) and SQL Server 2019 (15.x). For bulk operations only, LOCATION must be valid the URL to Azure Blob storage. Don't put /, file name, or shared access signature parameters at the end of the LOCATION URL. The credential you use must be created using SHARED ACCESS SIGNATURE as the identity. For more information on shared access signatures, see Using Shared Access Signatures (SAS).

Remarks

Only single source can be modified at a time. Concurrent requests to modify the same source cause one statement to wait. However, different sources can be modified at the same time. This statement can run concurrently with other statements.

In Azure Synapse Analytics, connections to external data sources pointing to Azure Blob storage or Azure Data Lake storage are supported in dedicated SQL pool only.

Permissions

Requires ALTER ANY EXTERNAL DATA SOURCE permission.

Important

The ALTER ANY EXTERNAL DATA SOURCE permission grants any principal the ability to create and modify any external data source object, and therefore, it also grants the ability to access all database scoped credentials on the database. This permission must be considered as highly privileged, and therefore must be granted only to trusted principals in the system.

Examples

The following example alters the location and Resource Manager location of an existing data source. Doesn't apply to SQL Server 2022 (16.x).

ALTER EXTERNAL DATA SOURCE hadoop_eds SET
     LOCATION = 'hdfs://10.10.10.10:8020',
     RESOURCE_MANAGER_LOCATION = '10.10.10.10:8032'
    ;

The following example alters the credential to connect to an existing data source.

ALTER EXTERNAL DATA SOURCE hadoop_eds SET
   CREDENTIAL = new_hadoop_user
    ;

The following example alters the credential to a new LOCATION. This example is an external data source created for Azure Synapse Analytics.

ALTER EXTERNAL DATA SOURCE AzureStorage_west SET
   LOCATION = 'wasbs://loadingdemodataset@updatedproductioncontainer.blob.core.windows.net',
   CREDENTIAL = AzureStorageCredential

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