Connect to CSV Data 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 CSV, you get access to your CSV data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live CSV data using T-SQL queries.

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

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

Configure CSV Connectivity for PolyBase

Connectivity to CSV from PolyBase is made possible through CData Connect AI. To work with CSV data from PolyBase, we start by creating and configuring a CSV connection.

1. Log into Connect AI, click Sources, and then click Add Connection
👁 Adding a Connection

2. Select "CSV" from the Add Connection panel
👁 Selecting a data source

3. Enter the necessary authentication properties to connect to CSV.

   Connecting to Local or Cloud-Stored (Box, Google Drive, Amazon S3, SharePoint) CSV Files

   CData Drivers let you work with CSV files stored locally and stored in cloud storage services like Box, Amazon S3, Google Drive, or SharePoint, right where they are.

   Setting connection properties for local files

   Set the URI property to local folder path.

   Setting connection properties for files stored in Amazon S3

   To connect to CSV file(s) within Amazon S3, set the URI property to the URI of the Bucket and Folder where the intended CSV files exist. In addition, at least set these properties:

   • AWSAccessKey: AWS Access Key (username)
   • AWSSecretKey: AWS Secret Key

   Setting connection properties for files stored in Box

   To connect to CSV file(s) within Box, set the URI property to the URI of the folder that includes the intended CSV file(s). Use the OAuth authentication method to connect to Box.

   Dropbox

   To connect to CSV file(s) within Dropbox, set the URI proprerty to the URI of the folder that includes the intended CSV file(s). Use the OAuth authentication method to connect to Dropbox. Either User Account or Service Account can be used to authenticate.

   SharePoint Online (SOAP)

   To connect to CSV file(s) within SharePoint with SOAP Schema, set the URI proprerty to the URI of the document library that includes the intended CSV file. Set User, Password, and StorageBaseURL.

   SharePoint Online REST

   To connect to CSV file(s) within SharePoint with REST Schema, set the URI proprerty to the URI of the document library that includes the intended CSV file. StorageBaseURL is optional. If not set, the driver will use the root drive. OAuth is used to authenticate.

   Google Drive

   To connect to CSV file(s) within Google Drive, set the URI property to the URI of the folder that includes the intended CSV file(s). Use the OAuth authentication method to connect and set InitiateOAuth to GETANDREFRESH.

   👁 Configuring a connection (Salesforce is shown)
   
4. Click Save & Test
5. Navigate to the Permissions tab in the Add CSV Connection page and update the User-based permissions. 👁 Updating permissions
   

Add a Personal Access Token

When connecting to Connect AI through the REST API, the OData API, or the Virtual SQL Server, a Personal Access Token (PAT) is used to authenticate the connection to Connect AI. It is best practice to create a separate PAT for each service to maintain granularity of access.

1. Click on the Gear icon () at the top right of the Connect AI app to open the settings page.
2. On the Settings page, go to the Access Tokens section and click Create PAT.
3. Give the PAT a name and click Create. 👁 Creating a new PAT
   
4. The personal access token is only visible at creation, so be sure to copy it and store it securely for future use.

With the connection configured and a PAT generated, you are ready to connect to CSV data from Polybase.

Create an External Data Source for CSV Data

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

Creating a Credential Database

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

NOTE: Set IDENTITY to your Connect AI username and set SECRET to your Personal Access Token.

CREATE DATABASE SCOPED CREDENTIAL ConnectCloudCredentials
WITH IDENTITY = 'yourusername', SECRET = 'yourPAT';

Create an External Data Source for CSV

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

CREATE EXTERNAL DATA SOURCE ConnectCloudInstance
WITH ( 
 LOCATION = 'sqlserver://tds.cdata.com:14333',
 PUSHDOWN = ON,
 CREDENTIAL = ConnectCloudCredentials
);

Create External Tables for CSV

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to CSV data from your SQL Server instance. The table column definitions must match those exposed by CData Connect AI. You can use the Data Explorer in Connect AI to see the table definition.

👁 Table definition in the Data Explorer (Salesforce is shown)

Sample CREATE TABLE Statement

Execute a CREATE EXTERNAL TABLE SQL command to create the external table(s), using the collation and setting the LOCATION to three-part notation for the connection, catalog, and table. The statement to create an external table based on a CSV Customer would look similar to the following.

CREATE EXTERNAL TABLE Customer(
 City COLLATE [nvarchar](255) NULL,
 TotalDue COLLATE [nvarchar](255) NULL,
 ...
) WITH ( 
 LOCATION='CSV1.CSV.Customer',
 DATA_SOURCE=ConnectCloudInstance
);

Having created external tables for CSV in your SQL Server instance, you are now able to query local and remote data simultaneously. To get live data access to hundreds of SaaS, Big Data, and NoSQL sources directly from your SQL Server database, try CData Connect AI today!