OCP-1Z0-053-V13.02-67题

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67.On which two database objects can the VERSIONS clause of the Flashback Versions Query be used?

(Choose two.)

A. fixed tables

B. heap tables

C. external tables

D. temporary tables

E. Index-Organized Tables (IOTs)

Answer: BE

答案解析：

同489题：http://blog.csdn.net/rlhua/article/details/19175515

参考：http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_10002.htm#SQLRF55624

排除法，选择BE

Restrictions on Flashback Queries These queries are subject to the following restrictions:

• You cannot specify a column expression or a subquery in the expression of the AS OF clause.

• You cannot specify the AS OF clause if you have specified the for_update_clause.

• You cannot use the AS OF clause in the defining query of a materialized view.

• You cannot use the VERSIONS clause in flashback queries to temporary or external tables, or tables that are part of a cluster.

• You cannot use the VERSIONS clause in flashback queries to views. However, you can use the VERSIONS syntax in the defining query of a view.

• You cannot specify the flashback_query_clause if you have specified query_name in the query_table_expression.

  
  
  
  

同489题

To research an erroneous change, you can use multiple Oracle Flashback queries to view row data at specific points in time. A more efficient approach would be to use Oracle Flashback Version Query to view all changes to a row over a period of time. With this feature, you append a VERSIONS clause to a SELECTstatement that specifies a system change number (SCN) or timestamp range between which you want to view changes to row values. The query also can return associated metadata, such as the transaction responsible for the change.

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