An access driver is an API that interprets the external data for the database. The access driver runs inside the database, which uses the driver to read the data in the external table. The access driver and the external table layer are responsible for performing the transformations required on the data in the data file so that it matches the external table definition.
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The following figure represents SQL access of external data.
Figure 2-8 External Tables
Description of “Figure 2-8 External Tables”
Oracle provides the following access drivers for external tables:
ORACLE_LOADER(default)Enables read-only access to external files using SQL*Loader. You cannot create, update, or append to an external file using theORACLE_LOADERdriver.
microsoft system center certification training courses malaysiaORACLE_DATAPUMPEnables you to unload or load external data. An unload operation reads data from the database and inserts the data into an external table, represented by one or more external files. After external files are created, the database cannot update or append data to them. A load operation reads an external table and loads its data into a database.
microsoft sql server certification training courses malaysiaORACLE_HDFSEnables the extraction of data stored in a Hadoop Distributed File System (HDFS).ORACLE_HIVEEnables access to data stored in an Apache Hive database. The source data can be stored in HDFS, HBase, Cassandra, or other systems. Unlike the other access drivers, you cannot specify a location becauseORACLE_HIVEobtains location information from an external metadata store.
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