Working with External Data

A newer version of this documentation is available. Use the version menu above to view the most up-to-date release of the Greenplum 6.x documentation.

Working with External Data

Both external and foreign tables provide access to data stored in data sources outside of Greenplum Database as if the data were stored in regular database tables. You can read data from and write data to external and foreign tables.

An external table is a Greenplum Database table backed with data that resides outside of the database. You create a readable external table to read data from the external data source and create a writable external table to write data to the external source. You can use external tables in SQL commands just as you would a regular database table. For example, you can SELECT (readable external table), INSERT (writable external table), and join external tables with other Greenplum tables. External tables are most often used to load and unload database data. Refer to Defining External Tables for more information about using external tables to access external data.

Accessing External Data with PXF describes using PXF and external tables to access external data sources.

A foreign table is a different kind of Greenplum Database table backed with data that resides outside of the database. You can both read from and write to the same foreign table. You can similarly use foreign tables in SQL commands as described above for external tables. Refer to Accessing External Data with Foreign Tables for more information about accessing external data using foreign tables.

Web-based external tables provide access to data served by an HTTP server or an operating system process. See Creating and Using External Web Tables for more about web-based tables.