External Tables [1]

 

An External Table :

• A read-only table
• Only meta-data is stored in the database
• No DML operations are possible, No indexes.
• CREATE TABLE AS SELECT statement is possible.
• Two major access drivers
  • ORACLE_LOADER
  • ORACLE_DATAPUMP : import and export data
    • CREATE TABLE AS SELECT statement is possible.
    • Read data from a table in the database and insert it into an external table.
    • After initial population, NO DML is possible.

Preceding work for Creating a Directory for the External Table

• Create a directory object where the external table will be located.

Examples)

CREATE OR REPLACE DIRECTORY emp_dir AS '/…/emp_dir';   GRANT REAN ON DIRECTORY emp_dir TO hr;

 

Syntax)

CREATE [OR REPLACE] DIRECTORY AS 'path_name';   In the syntax: Directory : the name of the directory object. Maximum length is 30 bytes.