How to connect PolyBase to SQL Server

PolyBase for SQL Server allows you to query external data by using the same Transact-SQL syntax used to query a database table. When paired with the CData ODBC Driver for SQL Server, you get access to your SQL Server data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live SQL Server data using T-SQL queries.

NOTE: PolyBase is only available on SQL Server 19 and above, and only for Standard SQL Server.

The CData ODBC drivers offer unmatched performance for interacting with live SQL Server data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to SQL Server, the driver pushes down supported SQL operations, like filters and aggregations, directly to SQL Server and utilizes the embedded SQL engine to process unsupported operations (often SQL functions and JOIN operations) client-side. And with PolyBase, you can also join SQL Server data with SQL Server data, using a single query to pull data from distributed sources.

Connect to SQL Server

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. To create an external data source in SQL Server using PolyBase, configure a System DSN (CData SQL Server Sys is created automatically).

Connecting to Microsoft SQL Server

Connect to Microsoft SQL Server using the following properties:

• Server: The name of the server running SQL Server.
• User: The username provided for authentication with SQL Server.
• Password: The password associated with the authenticating user.
• Database: The name of the SQL Server database.

Connecting to Azure SQL Server and Azure Data Warehouse

You can authenticate to Azure SQL Server or Azure Data Warehouse by setting the following connection properties:

• Server: The server running Azure. You can find this by logging into the Azure portal and navigating to "SQL databases" (or "SQL data warehouses") -> "Select your database" -> "Overview" -> "Server name."
• User: The name of the user authenticating to Azure.
• Password: The password associated with the authenticating user.
• Database: The name of the database, as seen in the Azure portal on the SQL databases (or SQL warehouses) page.

Click "Test Connection" to ensure that the DSN is connected to SQL Server properly. Navigate to the Tables tab to review the table definitions for SQL Server.

Create an External Data Source for SQL Server Data

After configuring the connection, you need to create a master encryption key and a credential database for the external data source.

Creating a Master Encryption Key

Execute the following SQL command to create a new master key, 'ENCRYPTION,' to encrypt the credentials for the external data source.

CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'password';

Creating a Credential Database

Execute the following SQL command to create credentials for the external data source connected to SQL Server data.

NOTE: IDENTITY and SECRET correspond with the User and Password properties for SQL Server.

CREATE DATABASE SCOPED CREDENTIAL sql_creds
WITH IDENTITY = 'sql_username', SECRET = 'sql_password';

Create an External Data Source for SQL Server

Execute a CREATE EXTERNAL DATA SOURCE SQL command to create an external data source for SQL Server with PolyBase:

• Set the LOCATION parameter , using the DSN and credentials configured earlier.

NOTE: SERVERNAME and PORT corresponds to the Server and Port connection properties for SQL Server. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

CREATE EXTERNAL DATA SOURCE cdata_sql_source
WITH ( 
  LOCATION = 'odbc://SERVERNAME[:PORT]',
  CONNECTION_OPTIONS = 'DSN=CData SQL Server Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = sql_creds
);

Create External Tables for SQL Server

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to SQL Server data from your SQL Server instance. The table column definitions must match those exposed by the CData ODBC Driver for SQL Server. You can refer to the Tables tab of the DSN Configuration Wizard to see the table definition.

Sample CREATE TABLE Statement

The statement to create an external table based on a SQL Server Orders would look similar to the following:

CREATE EXTERNAL TABLE Orders(
  ShipName [nvarchar](255) NULL,
  Freight [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Orders',
  DATA_SOURCE=cdata_sql_source
);

Having created external tables for SQL Server in your SQL Server instance, you are now able to query local and remote data simultaneously. Thanks to built-in query processing in the CData ODBC Driver, you know that as much query processing as possible is being pushed to SQL Server, freeing up local resources and computing power. Download a free, 30-day trial of the ODBC Driver for SQL Server and start working with live SQL Server data alongside your SQL Server data today.