Implement performance improvements in Dataflows

Query folding is an important optimization mechanism for dataflows. When query folding occurs, processing is done by the data source instead of Power Query. Query folding is primarily available to structured data sources such as a SQL database. Queries that rely solely on unstructured data sources or that don't have a compute engine, such as CSV files, don't have query folding capabilities.

In this exercise we'll load data from two different sources and see the difference in behavior due to query folding.

Note: If you get an error about an API rate limit, this usually happens because a previous Fabric task has not completed. You can view active Fabric tasks from the Monitor page (located on the left vertical menu). Canceling old Fabric tasks in the Monitor page will usually resolve the rate limit error.