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047-026

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-16 16:17:03 0 删除 编辑
26. Which statement is true regarding external tables?
A. The default REJECT LIMIT for external tables is UNLIMITED.
B. The data and metadata for an external table are stored outside the
database.
C. ORACLE_LOADER and ORACLE_DATAPUMP have exactly the same functionality
when used with an external table.
D. The CREATE TABLE AS SELECT statement can be used to unload data into regular
table in the database from an external table.
Answer: D
An external table is a read-only table that is defined within the database
but exists outside of the database. In more technical terms, the external
table’s metadata is stored inside the database, and the data it contains
is outside of the database. You can query them with the SELECT statement,
but you cannot use any other DML statements on them.You can’t create an INDEX
on them, and they won’t accept constraints.we specify that we are using
ORACLE_LOADER, aka the SQL*Loader features. An alternative(选择性) TYPE
value here would be ORACLE_DATAPUMP.

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