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You can submit custom SQL queries to relational or hive connections. These custom SQLs can be used to pre-filter the data inside the database, improving performance of the query and the overall dataset. For more information, see 

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Create Dataset with SQL

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Request Body:

Notes:

• See previous notes on queries to relational sources.
• As part of the request body, you must submit the custom SQL query as the value for the raw property.

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