Connect to AlloyDB 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 Cloud, linked servers provides instant access to AlloyDB data from your SQL Server database. This article demonstrates how to connect to AlloyDB using Connect Cloud and query AlloyDB data in SQL Server Management Studio (SSMS).

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

Configure AlloyDB Connectivity for SQL Server

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

1. Log into Connect Cloud, click Connections and click Add Connection
2. Select "AlloyDB" from the Add Connection panel
3. Enter the necessary authentication properties to connect to AlloyDB.

   The following connection properties are usually required in order to connect to AlloyDB.

   • Server: The host name or IP of the server hosting the AlloyDB database.
   • User: The user which will be used to authenticate with the AlloyDB server.
   • Password: The password which will be used to authenticate with the AlloyDB server.

   You can also optionally set the following:

   • Database: The database to connect to when connecting to the AlloyDB Server. If this is not set, the user's default database will be used.
   • Port: The port of the server hosting the AlloyDB database. This property is set to 5432 by default.

   Authenticating with Standard Authentication

   Standard authentication (using the user/password combination supplied earlier) is the default form of authentication.

   No further action is required to leverage Standard Authentication to connect.

   Authenticating with pg_hba.conf Auth Schemes

   There are additional methods of authentication available which must be enabled in the pg_hba.conf file on the AlloyDB server.

   Find instructions about authentication setup on the AlloyDB Server here.

   Authenticating with MD5 Authentication

   This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to md5.

   Authenticating with SASL Authentication

   This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to scram-sha-256.

   Authenticating with Kerberos

   The authentication with Kerberos is initiated by AlloyDB Server when the ∏ is trying to connect to it. You should set up Kerberos on the AlloyDB Server to activate this authentication method. Once you have Kerberos authentication set up on the AlloyDB Server, see the Kerberos section of the help documentation for details on how to authenticate with Kerberos.

4. Click Create & Test
5. Navigate to the Permissions tab in the Add AlloyDB Connection page and update the User-based permissions.

Add a Personal Access Token

If you are connecting from a service, application, platform, or framework that does not support OAuth authentication, you can create a Personal Access Token (PAT) to use for authentication. Best practices would dictate that you create a separate PAT for each service, to maintain granularity of access.

1. Click on your username at the top right of the Connect Cloud app and click User Profile.
2. On the User Profile page, scroll down to the Personal Access Tokens section and click Create PAT.
3. Give your 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.

Connect to AlloyDB from SQL Server using Connect Cloud

To establish a connection from SQL Server Linked Server to the CData Connect Cloud 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 Cloud data source you want to connect to (for example, AlloyDB1).
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 Cloud username. This is displayed in the top-right corner of the CData Connect Cloud interface. For example, test@cdata.com.
   • 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 AlloyDB linked server from any tool that can connect to SQL Server. An example SQL query would be: SELECT * FROM [CDATA CONNECT CLOUD].[AlloyDB1].[AlloyDB].[Orders] We have successfully created a linked server that allows us to query AlloyDB data.

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