# Data Sources In the Sources explorer you can find all the data sources available via the data warehouse connection that you have selected when creating the workflow. [Here](https://docs.carto.com/carto-user-manual/connections/introduction/) you can learn more about how to create your data warehouse connections in CARTO. There are three different types of data source: Connection data, Data Observatory and Files ### Connection data {% hint style="info" %} **Note** In case you are using a service account to connect to Google BigQuery, note that it must have at least BigQuery Data Editor (`roles/bigquery.dataEditor`) permissions in order to edit schemas, create and edit tables, and get information regarding jobs. {% endhint %} It is important to note that currently each workflow can only be associated with one single data warehouse connection and that it is defined at the time of creating the workflow (without being able to modify it afterwards). Through "Connection data" you will have access to tables in schemas/datasets in your data warehouse. These sources can be used in workflows by just adding them to the canvas. {% hint style="warning" %} While it is **supported to insert or update or data** in your table sources, **modifying the schema** of these tables (such as adding or removing columns, or changing data types) **may cause unexpected behavior or errors** during execution, as the schema won't be automatically updated in the workflow. \ If you expect schema changes in your tables, it is recommended to use a [**Custom SQL** **component**](https://docs.carto.com/carto-user-manual/components/custom#custom-sql-select) and explicitly specify the column names to reflect those changes throughout the workflow. {% endhint %} #### **CARTO Data Warehouse in non-US regions** If your CARTO organization has been provisioned in a cloud region outside of the US (Europe-West, Asia-Northeast or Australia-Southeast), you will be able to select between two different options in your *Sources* panel in Workflows: * **Your organization's region**. You will only have access to your own 'shared' and 'private' datasets within 'organization data'. * **CARTO's region (US)**. This one will grant to access to a different 'organization data' provisioned in the US region and also to CARTO's 'demo data'. ### Files If you want to use data that is not available via the data warehouse connection used in the workflow, you always have the possibility to **drag and drop files** to your workflow at any time which will get imported to your data warehouse via the established connection. Please find the list of supported file formats and size limits [here](https://docs.carto.com/carto-user-manual/data-explorer/importing-data#supported-formats). The files added by drag and drop, or selected from your browser will be stored and remain accessible from the same Workflow. {% hint style="success" %} You can star connections, database/projects/schemas and tables to quickly access them later. For more information, see [Starring items for quick access](https://docs.carto.com/data-explorer#starring-items-for-quick-access). {% endhint %}