单选题Which statement is true regarding Flashback Version Query？ （）A  It returns versions of rows only within a transaction.B  It can be used in subqueries contained only in a SELECT statement.C  It will return an error if the undo retention time is less tha

第1题：

Which three statements are true regarding subqueries?（）

• A、Subqueries can contain GROUP BY and ORDER BY clauses 
• B、Main query and subquery can get data from different tables 
• C、Main query and subquery must get data from the same tables 
• D、Subqueries can contain ORDER BY but not the GROUP BY clause 
• E、Only one column or expression can be compared between the main query and subquery
• F、 Multiple columns or expressions can be compared between the main query and subquery

第2题：

Which statements are true regarding the Query Result Cache？（） 

• A、 It can be set at the system， session， or table level.
• B、 It is used only across statements in the same session.
• C、 It can store the results from normal as well as flashback queries.
• D、 It can store the results of queries based on normal，temporary，and dictionary tables.

第3题：

Which of the following statements best describes Flashback Versions Query？（）  

• A、 Flashback Versions Query is used to make changes to multiple versions of data that existed between two points in time.
• B、 Flashback Versions Query is used to view all version changes on rows that existed between the time  the query was executed and a point in time in the past.
• C、 Flashback Versions Query is used to view version changes and the SQL to undo those changes on rows that existed between two points in time.
• D、 Flashback Versions Query is used to view all version changes on rows that existed between two  points in time.

第4题：

Which two statements are correct regarding the Flashback Versions Query feature？（）

• A、 You can use this feature to identify the committed versions of the rows， but not the uncommitted versions.
• B、 You can use this feature to identify the versions of V$ views.
• C、 You can use this feature to identify the inserts， deletes， and updates performed on a particular row but not the data definition language （DDL） operations performed on the table.
• D、 You can use this feature for a table only if row movement is enabled for the table.
• E、 You can use this feature to identify the versions of external and fixed tables.

第5题：

You executed the following query：  SELECT operation， undo_sql， table_name FROM flashback_transaction_query； Which statement is correct regarding the query output？（）

• A、 It would return information regarding only the last committed transaction.
• B、 It would return only the active transactions in all the undo segments in the database.
• C、 It would return only the committed transactions in all the undo segments in the database.
• D、 It would return both active and committed transactions in all the undo segments in the database.
• E、 It would return information regarding the transactions that began and were committed in the last 30 minutes.

第6题：

Which two statements are true about WHERE and HAVING clauses? （）

• A、A WHERE clause can be used to restrict both rows and groups.
• B、A WHERE clause can be used to restrict rows only.
• C、A HAVING clause can be used to restrict both rows and groups.
• D、A HAVING clause can be used to restrict groups only.
• E、A WHERE clause CANNOT be used in a query of the query uses a HAVING clause.
• F、A HAVING clause CANNOT be used in subqueries.

第7题：

Which two statements about subqueries are true? （）

• A、A subquery should retrieve only one row.
• B、A subquery can retrieve zero or more rows.
• C、A subquery can be used only in SQL query statements.
• D、Subqueries CANNOT be nested by more than two levels.
• E、A subquery CANNOT be used in an SQL query statement that uses group functions.
• F、When a subquery is used with an inequality comparison operator in the outer SQL statement, the column list in the SELECT clause of the subquery should contain only one column.

第8题：

You are employed as a DBA in an organization. You are informed that the record of EMP_NO 1000 is missing from the SCOTT.EMP table. You are required to identify the user who deleted the record， the SQL statement that will undo the deletion， and the transaction ID of the transaction that deleted the employee record. Which feature will you use to perform the tasks？（）

• A、 Only the Flashback Table
• B、 Both the Flashback Transaction Query and the Flashback Version Query
• C、 Only the Flashback Drop
• D、 Only the Flashback Version

第9题：

You are maintaining your OLTP database in Oracle10g. You are performing the Flashback Transaction Query to find the undo SQL statements that can be used to undo the changes made to the database in the specific time period. Which pseudocolumn will you use to perform the Flashback Transaction Query？（）

• A、 VERSIONS_STARTSCN
• B、 VERSIONS_STARTTIME
• C、 VERSIONS_XID
• D、 VERSIONS_OPERATION

第10题：

What is true regarding subqueries?（）

• A、The inner query always sorts the results of the outer query
• B、The outer query always sorts the results of the inner query
• C、The outer query must return a value to the outer query
• D、The inner query returns a value to the outer query
• E、The inner query must always return a value or the outer query will give an error