You cannot alter the external table schema.
不能改变外部表模式。
Create an external table using the following DDL.
使用以下ddl创建一个外部表。
Create the external table using the following query.
使用以下查询创建外部表。
LBAC security cannot be imposed on external table data files.
LBAC安全性不能施加在外部表数据文件上。
Select the rows from the external table using the query in Listing 11.
使用清单11中的查询选择外部表中的行。
An external table can be created using one of the following three methods.
外部表可以采用以下三种方法创建。
NUMROWS: the approximate number of rows that the external table can possibly have.
NUMROWS：外部表可能拥有的大致行数。
NUMROWS is used to provide an approximate number of rows that an external table can have.
NUMROWS用于提供一个外部表可能拥有的大致行数。
Using a select statement to select from a data source into an external table (see Listing 3).
使用select语句从一个数据源选择构成外部表的数据(参见清单3)。
Note that at the time of creating an external table, the data files associated with the external table need not exist.
注意，在外部表创建之时，与该外部表关联的数据文件不需要存在。
DATAFILES is a mandatory clause for each external table. It specifies the file path where the data can be read from or written to.
DATAFILES是每个外部表的必需子句，它指定读写数据的文件路径。
To create an external table "et_customer" with the same schema as customer table with a delimiter "|", you can use the following DDL statement.
要使用分隔符“|”创建与customer表具有相同表模式的外部表“et_customer”，可以使用以下ddl语句。
The example code in Listing 19 creates a distinct user-defined type called "birthday" and is being used as the column type while creating the external table.
清单19中的示例代码创建了一个明显的名为“birthday”的用户定义类型，并在创建外部表时用作列类型。
Support of external table creation, access, load, and unload from within the stored procedures makes it easier to perform the batch load and unload operations.
存储过程中的外部表创建、访问、加载和卸载支持允许您更轻松地执行批加载和卸载操作。
Selecting from an external table reads the data from the data file(s) and provides it in the form of rows and columns as if it was read from the normal base table.
从外部表选择可从一个或多个数据文件读取数据，并以行和列的形式提供该数据，就好像从常规基表读取数据一样。
If the base table to which the data is loaded from the external table is defined to be a RAW table without indexes, the IDS server USES light appends to load the data.
如果将从外部表加载数据所到的基表定义为不带索引的raw表，则IDS服务器将使用“轻追加法”加载数据。
External table "et_state" does not keep the reference to the template table "state"; meaning that, when the state table is later modified, the external table is not affected.
外部表“et_state”并不保持对模板表“state”的引用，即，state表稍后有改动时，这个外部表不受影响。
External table statements can also be used as static statements.
外部表语句也可以用作静态语句。
External table data files are excluded from all forms of replication.
外部表数据文件不能进行任何形式的复制。
Using the CREATE EXTERNAL TABLE statement with column specification (see Listing 1).
使用带有列指定的CREATEEXTERNAL table语句(参见清单1)。
Using the CREATE EXTERNAL TABLE statement with column specification (see Listing 1).
使用带有列指定的CREATEEXTERNAL table语句(参见清单1)。
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