10gCR-Chapter 26 External table

You can use the external table feature to access external files as if they were tables inside the database. When you create an external table, you define its structure and location within Oracle. When you query the table, Oracle reads the external table and returns the results just as if the data had been stored within the database. But because the data is outside the database, you do not have to be concerned about the process for loading it into the database—a potentially significant benefit for data warehouses and large databases.

你可以使用外部表特性去访问OS上的其它文件，好像他们就是数据库中的表一样。当你建立一个外部表时，你在oralce中定义它的结构和位置。当你查询这个表时，oracle读取外部表，并且像不同表一样返回数据。你不必因为数据是存储在数据库之外的，而考虑数据装载入数据库的过程--对数据仓库和大型数据库来说是潜在的意义重大的好处。

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