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Connect to OData as an External Data Source using PolyBase

Use the CData ODBC Driver for OData and PolyBase to create an external data source in SQL Server 2019 with access to live OData services.

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 OData, you get access to your OData services directly alongside your SQL Server data. This article walks through creating an external data source and external tables to grant access to live OData services using T-SQL queries.

The CData ODBC drivers offer unmatched performance for interacting with live OData services using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to OData, the driver pushes down supported SQL operations, like filters and aggregations, directly to OData 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 OData services, using a single query to pull data from distributed sources.

Connect to OData

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 OData Sys is created automatically).

The User and Password properties, under the Authentication section, must be set to valid OData user credentials. In addition, you will need to specify a URL to a valid OData server organization root or OData services file.

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

Create an External Data Source for OData Services

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 OData services.

NOTE: Since OData does not require a User or Password to authenticate, you may use whatever values you wish for IDENTITY and SECRET.

CREATE DATABASE SCOPED CREDENTIAL odata_creds
WITH IDENTITY = 'username', SECRET = 'password';

Create an External Data Source for OData

Execute the following SQL command to create an external data source for OData with PolyBase, using the DSN and credentials configured earlier.

For OData, set SERVERNAME to 'localhost' or '127.0.0.1' and leave PORT empty. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

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

Create External Tables for OData

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

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

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