【Oracle OCP考试】1z0-082（2）

1.Which two statements are true about views used for viewing tablespace and datafile information? (Choose two)

A . Tablespace free space can be viewed in V$TABLESPACE

B . V$TABLESPACE displays information that is contained in the
controlfile about tablespaces

C . V$TABLESPACE displays information about tablespaces contained in
the data dictionary
D . Tablespace free space can be viewed in DBA_TABLESPACES
E . A datafile can be renamed when the database is in MOUNT state and the new file name is displayed when querying DBA_DATA_FILES after the database is opened

标准答案 :BE

2.Which three statements are true about views in an Oracle Database?(Choose three)

A . Rows inserted into a table using a view are retained in the table
if the view is dropped.
B . A view can be created that refers to a non-existent table in its defining query.
C . Views have no object number.
D . Views have no segment.
E . A SELECT statement cannot contain a WHERE clause when querying a view containing a WHERE clause in its defining query.
F . Views can join tables only if they belong to the same schema.

标准答案:ABD

3.Which two statements are true about views?(choose two)

A . Views can be updated without the need to re-grant privileges on
the view.
B . Views can be indexed.
C . The WITH CHECK clause prevents certain rows from being updated or inserted in the underlying table through the view.
D . The WITH CHECK clause prevents certain rows from being displayed when querying the view.
E . Tables in the defining query of a view must always exist in order to create the view.

标准答案 :AC

4.Which two statements are true about views?

A. A view must only refer to tables in its defining query.
B. The WITH CHECK clause prevents certain rows from being displayed when querying the view
C. Views can be updated without the need to re-grant privileges on the view
D. The WITH CHECK clause prevents certain rows from being updated or inserted in the underlying table through the view.
E. Views can be indexed

标准答案 :CD

【总结】
1.V$TABLESPACE，也叫做“表空间视图”，是Oracle数据库中的一个系统视图，它包含了当前实例上每个表空间的当前信息，以及表空间、段和文件的详细信息。它常用来检查表空间和文件的当前状态以及检查表空间使用情况等。

V$TABLESPACE的使用方法：

（1）查看表空间的信息：

SELECT ts.tablespace_name,
ts.status,
tf.file_name,
tf.bytes / 1024 / 1024 文件大小,
tf.autoextensible,
tf.maxbytes / 1024 / 1024 最大文件大小
FROM v$tablespace ts, v$datafile tf
WHERE ts.ts# = tf.ts#;

（2）查询表空间的使用情况：

SELECT ts.tablespace_name,
ts.contents,
ts.extent_management,
ts.allocation_type,
df.bytes / 1024 / 1024 空间大小,
nvl(sum(dfs.bytes) / 1024 / 1024, 0) 已使用,
nvl(sbts.bytes / 1024 / 1024, 0) 空闲空间
FROM v$tablespace ts, v$datafile df, v$tablespace_usage_metrics dfs, v$sort_segment sbts
WHERE ts.ts# = df.ts#
AND dfs.tablespace_id (+) = df.ts#
AND sbts.tablespace_id (+) = df.ts#
AND dfs.tablespace_name (+) = ts.tablespace_name
GROUP BY ts.tablespace_name, ts.contents, ts.extent_management, ts.allocation_type, df.bytes, nvl(sbts.bytes, 0);

2.无需重新授予视图权限即可更新视图。
3.WITH CHECK子句防止某些行通过视图更新或插入到基础表中。
4.视图没有段，有对象编号，不能被索引。