Error "You can only query existing data extensions or system data views"

When building a query in DESelect that uses Data Views, you may get the following error:

Error creating Preview DataExtension: Error saving the Query field._Subscribers is not a known data extension or system data view. You can only query existing data extensions or system data views.

_Subscribers may be replaced with any other data views.

This error happens if querying on Data Extensions is not enabled in your Marketing Cloud instance.

This can be solved in 2 ways:

- Log a case with Salesforce support and ask them to enable querying Data Views in your instance. Once they confirm it's enabled, you'll be able to run the query in DESelect without problems.

- If you don't want users in DESelect querying Data Views, log a case with DESelect support to disable querying Data Views. Data Views can be hidden from Available Data Extensions, so users can't use them.