Semab Tariq uses a Postgres extension:
The file_fdw (Foreign Data Wrapper) is a PostgreSQL extension that lets you access data stored in flat files, like CSV files, as if they were regular tables in your PostgreSQL database. This is useful for integrating external data sources without needing to import the data directly into your database.
file_fdw is a contrib module, meaning it’s an additional feature included with PostgreSQL but not part of its core functionality. Contrib modules provide extra capabilities and enhancements beyond the core database system.
At first, I was going to write that the mechanism looks a lot like PolyBase in SQL Server. But in actuality, it’s more like a hybrid of PolyBase and OPENROWSET, as there’s no definition of external data sources or file formats, but there is the creation of an external (“foreign”) table.