Connect to SFTP Data as a Linked Server via SQL Gateway

You can use the SQL Gateway to configure a TDS (SQL Server) remoting service and set up a linked server for SFTP data. After you have started the service, you can use the UI in SQL Server Management Studio or call stored procedures to create the linked server. You can then work with SFTP data just as you would a linked SQL Server instance.

Connect to SFTP as an ODBC Data Source

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

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.

Configure the TDS Remoting Service

See the SQL Gateway Overview for a guide to configure a TDS remoting service in the SQL Gateway UI. The TDS remoting service is a daemon process that listens for TDS requests from clients.

Create a Linked Server for SFTP Data

After you have configured and started the daemon, create the linked server and connect. You can use the UI in SQL Server Management Studio or call stored procedures.

Create a Linked Server from the UI

Follow the steps below to create a linked server from the Object Explorer.

1. Open SQL Server Management Studio and connect to an instance of SQL Server.
2. In the Object Explorer, expand the node for the SQL Server database. In the Server Objects node, right-click Linked Servers and click New Linked Server. The New Linked Server dialog is displayed.
3. In the General section, click the Other Data Source option and enter the following information after naming the linked server:
   • Provider: Select "Microsoft ODBC Driver for SQL Server" or "Microsoft OLE DB Driver for SQL Server"

   • Data Source: Enter the host and port the TDS remoting service is running on, separated by a comma.

     Note that a value of "localhost" in this input refers to the machine where SQL Server is running so be careful when creating a linked server in Management Studio when not running on the same machine as SQL Server.

   • Catalog:
     • Option 1: If you enabled the "Support multiple catalogs and schemas" option while creating and configuring the TDS Remoting Service in previous steps, enter CData as the catalog.
     • Option 2: For single schema support, enter the name of the data source's system DSN as CData SFTP Sys.
     👁 Linked Server properties (Salesforce is shown)
     
   • In the Security section, select the option to have the connection "made using this security context" and enter the username and password of a user you created in the Users tab of the SQL Gateway. 👁 A user known to the daemon in the Linked Server security properties.
     

Create a Linked Server Programmatically

In addition to using the SQL Server Management Studio UI to create a linked server, you can use stored procedures. The following inputs are required:

• server: The linked server name.
• provider: Enter "MSOLEDBSQL", for the Microsoft OLE DB Driver for SQL Server.

• datasrc: The host and port the service is running on, separated by a comma.

  Note that a value of "localhost" in the datasrc input refers to the machine where SQL Server is running, so be careful when creating a linked server in Management Studio when not running on the same machine as SQL Server.

• catalog: Enter the system DSN configured for the service.
• srvproduct: Enter the product name of the data source; this can be an arbitrary value, such as "CData SQL Gateway" or an empty string.

Follow the steps below to create the linked server and configure authentication to the SQL Gateway:

1. Call sp_addlinkedserver to create the linked server:

   EXEC sp_addlinkedserver @server='SFTP',
    @provider='MSOLEDBSQL',
    @datasrc='< MachineIPAddress >,1434',
    @catalog='CData SFTP Sys',
    @srvproduct='';
   GO
   

2. Call the sp_addlinkedsrvlogin stored procedure to allow SQL Server users to connect with the credentials of an authorized user of the service. Note that the credentials you use to connect to the service must specify a user you configured on the Users tab of the SQL Gateway.

   EXEC sp_addlinkedsrvlogin @rmtsrvname='SFTP',
    @rmtuser='admin',
    @rmtpassword='test',
    @useself='FALSE',
    @locallogin=NULL;
   GO
   

Connect from SQL Server Management Studio

SQL Server Management Studio uses the SQL Server Client OLE DB provider, which requires the ODBC driver to be used inprocess. You must enable the "Allow inprocess" option for the SQL Server Native Client Provider in Management Studio to query the linked server from SQL Server Management Studio. To do this, open the properties for the provider you are using under Server Objects -> Linked Servers -> Providers. Check the "Allow inprocess" option and save the changes.

Execute Queries

You can now execute queries to the SFTP linked server from any tool that can connect to SQL Server. Set the table name accordingly:

SELECT * FROM [linked server name].[CData SFTP Sys].[SFTP].[MyDirectory]

👁 The result of a query in SQL Server Management Studio. (Salesforce is shown.)