OCP-1Z0-051 第20题 oracle数据类型

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一、原题Which three statements are true regarding the data types in Oracle Database 10g/11g? (Choose three.)
A. Only one LONG column can be used per table.
B. A TIMESTAMP data type column stores only time values with fractional seconds.
C. The BLOB data type column is used to store binary data in an operating system file.
D. The minimum column width that can be specified for a VARCHAR2 data type column is one.
E. The value for a CHAR data type column is blank-padded to the maximum defined column.

答案  A、D、E

二、题目翻译关于Oracle Database 10g/11g中的数据类型，哪三个语句是正确的？（选择三个正确选项）
A. 每个表中只能使用一个LONG列。
B. 一个TIMESTAMP数据类型列只能存储带有小数秒的时间值。
C. BLOG数据类型列被用于存储二进制数据的操作系统文件。
D. VARCHAR2数据类型最小的列宽可以为1。
E. CHAR数据类型列的值是用空格填充到列定义的最大值（即：如果定义了CHAR(10),而字符串长度不够10个，则用空格填充不够的位数，CHAR为固定长度数据类型。

三、题目解析B选项不正确，因为TIMESTAMP可以存储不带有小数秒的日期或时间。
详细内容参考联机文档关于TIMSTAMP的解释：
          http://docs.oracle.com/cd/E11882_01/server.112/e41084/sql_elements001.htm#SQLRF00203
        The TIMESTAMP data type is an extension of the DATE data type. It stores the year, month, and day of the DATE data type, plus hour, minute, and second values.

C选项不正确，因为BLOB存储的是非结构化的二进制大对象。
详细内容参考联机文档关于BLOB的解释：
          http://docs.oracle.com/cd/E11882_01/server.112/e41084/sql_elements001.htm#SQLRF50997
       The BLOB data type stores unstructured binary large objects. BLOB objects can be thought of as bitstreams with no character set semantics. BLOB objects can store binary dataup to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage). If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK parameter of LOB storage when creating a LOB column, then this isequivalent to (4 gigabytes - 1) * (database block size).
        BLOB objects have full transactional support. Changes made through SQL, the DBMS_LOB package, or Oracle Call Interface (OCI) participate fully in the transaction. BLOB value manipulations can be committed and rolled back. However, you cannot save aBLOB locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
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