You find this query being used in your Oracle 12c database: Which method a used by the optimizer to limit the rows being returned?（）A、A filter is added to the table query dynamically using ROWNUM to limit the rows to 20 percent of the total rowsB、All the

题目

You find this query being used in your Oracle 12c database: Which method a used by the optimizer to limit the rows being returned?（）

A、A filter is added to the table query dynamically using ROWNUM to limit the rows to 20 percent of the total rows
B、All the rows are returned to the client or middle tier but only the first 20 percent are returned to the screen or the application.
C、A view is created during execution and a filter on the view limits the rows to 20 percent of the total rows.
D、A TOP-N query is created to limit the rows to 20 percent of the total rows

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相似问题和答案

第1题：

EIGRP is being used as the routing protocol on the PassGuide network. Whiletroubleshooting some network connectivity issues，you notice a large number of EIGRP SIA（StuckinActive）messages. What causes these SIA routes（）

A、The neighboring router stops receiving ACK packets from this router.
B、The neighboring router starts receiving route updates from this router.
C、The neighboring router is too busy to answer the query(generally caused by high CPU utilization).
D、The neighboring router is having memory problems and cannot allocate the memory to process the query or build the reply packet.

正确答案:C,D

第2题：

EIGRP is being used as the routing protocol on the company network. While troubleshooting somenetwork connectivity issues， you notice a large number of EIGRP SIA （Stuck in Active） messages.What causes these SIA routes？（）

A、The neighboring router stops receiving ACK packets from this router
B、The neighboring router starts receiving route updates from this router
C、The neighboring router is too busy to answer the query （generally caused by high CPUutilization）
D、The neighboring router is having memory problems and cannot allocate the memory to processthe query or build the reply packet

正确答案:C,D

第3题：

View the Exhibit for some of the parameter settings. You start a session and issue the following command:SQL>CREATE INDEX emp_ename ON emp(ename) TABLESPACE users INVISIBLE;What is the outcome of the above command?（）

A. The index is not used by the optimizer but is maintained during DML operations.

B. The index is not used by the optimizer and is not maintained during DML operations.

C. The index is used by the optimizer only if a hint is specified in the query statement and is maintained during DML operations.

D. The index is used by the optimizer only if a hint is specified in the query statement but is not maintained during DML operations.

参考答案：A

第4题：

You are required to flashback your database. You want to find the amount of flashback data generated since the database was opened. Which task will you perform to obtain the required information？（）

A、 Query the V$FLASHBACK_DATABASE_LOG view.
B、 Query the V$FLASHBACK_DATABASE_STAT view.
C、 Check the value of the DB_FLASHBACK_RETENTION_TARGET initialization parameter.
D、 Query the V$RECOVERY_FILE_DEST view.

正确答案:B

第5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

正确答案:C

第6题：

You have been assigned to manage a set of databases. The previous DBA did not leave you notes regarding the structure of each of the databases. While analyzing an instance， you notice that the system identifier （SID） for the instance is set to ’+ASM’. What is the purpose of this instance？（）

A、 This instance is being used to manage the operating system files.
B、 This instance is being used to manage the files of other databases.
C、 This instance is being used to manage the instances of other databases.
D、 This instance is being used to manage the background processes of other instances.

正确答案:B

第7题：

Examine the parameter for your database instance: You generated the execution plan for the following query in the plan table and noticed that the nested loop join was done. After actual execution of the query, you notice that the hash join was done in the execution plan: Identify the reason why the optimizer chose different execution plans.（）

A、The optimizer used a dynamic plan for the query.
B、The optimizer chose different plans because automatic dynamic sampling was enabled.
C、The optimizer used re-optimization cardinality feedback for the query.
D、The optimizer chose different plan because extended statistics were created for the columns used.

正确答案:B

第8题：

You define a multiple－row subquery in the WHERE clause of an SQL query with a comparison operator "=". What happens when the main query is executed? ()

A. The main query executes with the first value returned by the subquery.

B. The main query executes with the last value returned by the subquery.

C. The main query executes with all the values returned by the subquery.

D. The main query fails because the multiple-row subquery cannot be used with the comparison operator.

E. You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

参考答案：D

第9题：

You issued the following statement to monitor the usage of the index： SQL> ALTER INDEX SCOTT.EMP_IDX MONITORING USAGE； Which view will you query to ensure that the index is being monitored？（）

A、 INDEX_STATS
B、 DBA_INDEXES
C、 DBA_IND_COLUMNS
D、 V$OBJECT_USAGE

正确答案:D

第10题：

You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=".What happens when the main query is executed?（）

A、The main query executes with the first value returned by the subquery.
B、The main query executes with the last value returned by the subquery.
C、The main query executes with all the values returned by the subquery.
D、The main query fails because the multiple-row subquery cannot be used with the comparison operator.
E、You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

正确答案:D

You find this query being used

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