Editing PostgreSQL (section)

=== Foreign data wrappers ===
PostgreSQL can link to other systems to retrieve data via foreign data wrappers (FDWs).<ref>{{cite book
 |last1=Obe
 |first1=Regina
 |last2=Hsu
 |first2=Leo S.
 |chapter=10: Replication and External Data
 |title=PostgreSQL: Up and Running
 |url=https://books.google.com/books?id=Q8jkIZkMTPcC
 |edition=1
 |location=Sebastopol, CA
 |publisher=[[O'Reilly Media|O'Reilly Media, Inc.]]
 |date=2012
 |page=129
 |isbn=978-1-4493-2633-3
 |access-date=October 17, 2016
 |quote=Foreign Data Wrappers (FDW) [...] are mechanisms of querying external datasources. PostgreSQL 9.1 introduced this [[SQL/MED]] standards compliant feature.
}}</ref>
These can take the form of any data source, such as a file system, another [[relational database]] management system (RDBMS), or a web service. This means that regular database queries can use these data sources like regular tables, and even join multiple data-sources together.