Connect to Oracle as an External Data Source using PolyBase

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 Oracle, you get access to your Oracle data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live Oracle 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 Oracle data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to Oracle, the driver pushes down supported SQL operations, like filters and aggregations, directly to Oracle 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 Oracle data, using a single query to pull data from distributed sources.

Connect to Oracle

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 Oracle Sys is created automatically).

To connect to Oracle, you'll first need to update your PATH variable and ensure it contains a folder location that includes the native DLLs. The native DLLs can be found in the lib folder inside the installation directory. Once you've done this, set the following to connect:

• Port: The port used to connect to the server hosting the Oracle database.
• User: The user Id provided for authentication with the Oracle database.
• Password: The password provided for authentication with the Oracle database.
• Service Name: The service name of the Oracle database.

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

Create an External Data Source for Oracle 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 Oracle data.

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

CREATE DATABASE SCOPED CREDENTIAL oracleoci_creds
WITH IDENTITY = 'oracleoci_username', SECRET = 'oracleoci_password';

Create an External Data Source for Oracle

Execute a CREATE EXTERNAL DATA SOURCE SQL command to create an external data source for Oracle 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 Oracle. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

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

Create External Tables for Oracle

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to Oracle data from your SQL Server instance. The table column definitions must match those exposed by the CData ODBC Driver for Oracle. 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 Oracle Customers would look similar to the following:

CREATE EXTERNAL TABLE Customers(
  CompanyName [nvarchar](255) NULL,
  City [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Customers',
  DATA_SOURCE=cdata_oracleoci_source
);

Having created external tables for Oracle 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 Oracle, freeing up local resources and computing power. Download a free, 30-day trial of the ODBC Driver for Oracle and start working with live Oracle data alongside your SQL Server data today.