Connect to SFTP Data as a SQL Server Linked Server

SQL Server Linked Servers enable the SQL Server Database Engine to read data from remote data sources and execute commands against the remote database servers outside of the instance of SQL Server. Typically, linked servers are configured to enable the execution of a T-SQL statement that includes tables in another instance of SQL Server, or another database product such as Oracle. When paired with CData Connect AI, linked servers provides instant access to SFTP data from your SQL Server database. This article demonstrates how to connect to SFTP using Connect AI and query SFTP data in SQL Server Management Studio (SSMS).

CData Connect AI provides a pure SQL Server interface for SFTP, allowing you to query data from SFTP without replicating the data to a natively supported database. Using optimized data processing out of the box, CData Connect AI pushes all supported SQL operations (filters, JOINs, etc.) directly to SFTP, leveraging server-side processing to return the requested SFTP data quickly.

Configure SFTP Connectivity for SQL Server

Connectivity to SFTP from SQL Linked Servers is made possible through CData Connect AI. To work with SFTP data from SQL Linked Servers, we start by creating and configuring a SFTP connection.

1. Log into Connect AI, click Sources, and then click Add Connection

2. Select "SFTP" from the Add Connection panel

3. Enter the necessary authentication properties to connect to SFTP.

   SFTP can be used to transfer files to and from SFTP servers using the SFTP Protocol. To connect, specify the RemoteHost;. service uses the User and Password and public key authentication (SSHClientCert). Choose an SSHAuthMode and specify connection values based on your selection.

   Set the following connection properties to control the relational view of the file system:

   • RemotePath: Set this to the current working directory.
   • TableDepth: Set this to control the depth of subfolders to report as views.
   • FileRetrievalDepth: Set this to retrieve files recursively and list them in the Root table.
   Stored Procedures are available to download files, upload files, and send protocol commands. See gdatamodel for more on using SQL to interact with the server.
4. Click Save & Test
5. Navigate to the Permissions tab in the Add SFTP Connection page and update the User-based permissions.

Add a Personal Access Token

When connecting to Connect AI through the REST API, the OData API, or the Virtual SQL Server, a Personal Access Token (PAT) is used to authenticate the connection to Connect AI. It is best practice to create a separate PAT for each service to maintain granularity of access.

1. Click on the Gear icon () at the top right of the Connect AI app to open the settings page.
2. On the Settings page, go to the Access Tokens section and click Create PAT.
3. Give the PAT a name and click Create.
4. The personal access token is only visible at creation, so be sure to copy it and store it securely for future use.

With the connection configured and a PAT generated, you are ready to connect to SFTP data from .

Connect to SFTP from SQL Server using Connect AI

To establish a connection from SQL Server Linked Server to the CData Connect AI Virtual SQL Server API, follow these steps.

1. Open Microsoft SQL Server Management Studio.
2. In the Object Explorer pane, open Server Objects, right-click Linked Servers, and select New Linked Server.

3. The New Linked Server dialogue opens. On the General page, enter the following information:
   • Enter a name for the server in the Linked server field.
   • Select the radio button Other data source and select SQL Server Native Client 11.0 as the provider.
   • In the Data source field, enter tds.cdata.com,14333
   • In the Catalog field, enter enter the Connection Name of the CData Connect AI data source you want to connect to (for example, SFTP1).
   
4. Select the Security page. At the bottom, select the radio button labeled Be made using this security context and enter the following information:
   • Remote login - enter your CData Connect AI username. This is displayed in the top-right corner of the CData Connect AI interface. For example, [email protected].
   • With password - enter the PAT you generated on the Settings page.
   
5. Click OK to create the server.
Your linked server can now be used to access the data in the data source you specified. If you need to access data from more sources, create another linked server for each one.

Execute Queries

You can now execute queries to the SFTP linked server from any tool that can connect to SQL Server. An example SQL query would be:

		SELECT * FROM [CDATA CONNECT CLOUD].[SFTP1].[SFTP].[MyDirectory]
	

We have successfully created a linked server that allows us to query SFTP data.

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