[bbk5123] 第101集 第12章 数据移植 07

Oracle 数据引擎

• ORACLE_LOADER 用户只能从外部读取表数据，但是不能将数据库中的数据卸载到操作系统文件中.
• ORACLE_DATAPUMP 用户不仅可以从外部表中读取数据，同时可以将数据库中复杂的数据查询后卸载到操作系统文件中.

External Tables

External tables are read-only tables stored as files on the operating outside of the Oracle database.

External Table Benefits

• Data can be used directly from the external file or loaded into another database.
• External data can be queried and joined directly in parallel with tables residing in the databas ,without requiring it to be loaded first.
• The results of a complex query can be unloaded to an external file.
• You can combine generated files from different sources for loading purposes.

Defining an External Tables with ORACLE_LOADER

External Table Population with ORACLE_DATAPUMP

Using External Tables

• Querying and external table:

SQL>SELECT * FROM extab_employees;

• Querying and joining an external table with an internal table

SQL>SELECT e.employee_id,e.first_name,e.last_name,d.department_name 

        FROM departments d,extab_employees e

        WHERE d.department_id = e.department_id;

• Appending data to an internal table from an external table

SQL>INSERT /*+ APPEND*/ INTO hr.employees SELECT * FROM extab_employees;

Summary

In this lesson,you should have learned how to:

• Describe ways to move data
  • DATA PUMP
  • SQL LOADER
  • EXTERNAL TABLE
• Use SQL*Loader to load data from a non-Oracle database (or user files)
• Use external tables to move data via platform-independent files
• Explain the general architecture of Oracle Data Pump
• Use Data Pump Export and Import to move data between Oracle databases.