> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cloud.cdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Polybase

> This page outlines the steps to connect Polybase to Connect AI. Ensure Polybase has been installed and enabled before beginning these steps.

<Steps>
  <Step>
    Create a database scoped `CREDENTIAL` for connecting to the SQL Server. It should map `IDENTITY` and `SECRET` to your database's Username and Password respectively. Follow the example below.

    ```sql theme={null}
    CREATE DATABASE SCOPED CREDENTIAL SqlServerCredentials
     WITH IDENTITY = 'yourusername', SECRET = 'yourpassword';
    ```
  </Step>

  <Step>
    Using `CREATE EXTERNAL DATASOURCE`, create an external datasource that names the instance, identifies the external data source, and sets whether computation should be pushed via `PUSHDOWN` to source by default. This uses the `CREDENTIAL` created above. Use the below example as a template.

    ```sql theme={null}
    CREATE EXTERNAL DATA SOURCE SQLServerInstance
     WITH ( LOCATION = 'sqlserver://tds.cdata.com:14333',
     PUSHDOWN = ON,
     CREDENTIAL = SQLServerCredentials);
    ```
  </Step>

  <Step>
    Create the external table using `CREATE EXTERNAL TABLE`. The statement needs collation and the location must be in three-part notation `<database>.<schema>.<table>`. See below for a functional example.

    ```sql theme={null}
    CREATE EXTERNAL TABLE DatabasesExternal (
         name VARCHAR(128) COLLATE SQL_Latin1_General_CP1_CI_AS)
       WITH (LOCATION = 'QuickBooksOnline1.QuickBooksOnline.Accounts',
       DATA_SOURCE = SQLServerInstance);
    ```
  </Step>

  <Step>
    For optimal query performance, you can create statistics on external table columns, as per the code example below.

    ```sql theme={null}
    CREATE STATISTICS statistics_name ON customer (C_CUSTKEY)
     WITH FULLSCAN;
    ```
  </Step>
</Steps>