You can access and query external data by mounting catalogs. This feature uses a simple SQL syntax that is similar to how you query data using database links.

The simplified SQL syntax makes it easy to discover and query external data without having to choose which external data to access, and without having to construct external tables or perform any other data integration tasks.

Refer to the Query External Data chapter for more information.

By querying remote catalogs and databases, you are accessing data directly from the external catalog in place, without having to move data into the Autonomous Database. This feature enables you to export data from the catalogs that the Autonomous Database can access without establishing multiple connections. You can query the Autonomous Database to see which external catalogs are available, what data is available for any given catalog, and you can query the data directly, from any SQL client. This involves providing a standard and simplified way to discover and query data sets connected to the Autonomous Database, leveraging the catalog's ability to present external data as standard Oracle schemas and tables.

Refer to the Manage Catalogs chapter for information on catalogs supported across various categories, including Databases, External Data Catalogs, Shares, and more.

Some of the key features are:

• Discover External Data: Using SQL, you can identify external catalogs along with the tables they contain. This will help you in understanding the available data structure.
• Simplify Table Discovery: Use existing query syntax and familiar views to easily list tables within an external catalog.
• Integrate with data tools: You can integrate the query data with Data Studio suite of tools to make informed decisions and gain deeper insights.

Topics:

• Conceptual Diagram of Querying Remote Catalogs
  The following diagram displays the conceptual network diagram of querying remote catalogs using Autonomous Database:
• Concepts Related to Querying Remote Catalogs and Databases
  An understanding of the following concepts is necessary for querying with Remote Catalogs:
• About Querying Remote Catalogs and Databases
  This topic describes how to query external data using the catalog metadata using an SQL syntax of the form: [schema].object@catalog_name.
• Examples: List the Mounted Catalogs
  You will use this syntax in a SQL query.
• Examples: List the Tables in a Catalog, Including Their Owning Schemas
  To list all tables within a specific schema (catalog) from the enabled catalogs, you can use:
• Examples: Query Data from a Table in a Catalog
  To query data from a table in a specific catalog (schema), you must prepend the schema name to the table name.
• Examples: Query a Table from a Delta Share and Analyze the View
  Let’s assume that we are working on an inventory database where we have data about the information collected by the U.S. Census Service concerning housing in the Boston area, and we need a query that returns the maximum value of the full-value property tax.