单选题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 t

第1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.

第2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3题：

You work as a database administrator for Supportcenter.cn. One of the database users accidentally deleted all the rows of a critical table and committed the delete at 1：30 p.m. You senior database administrator， SupportCenter， asks you to retrieve the lost data. Which two actions would you use to ensure that there is no impact on other connected users while retrieving the deleted rows？（）

• A、Use a flashback query to retrieve the rows that were deleted
• B、Useconventialincremental export and then import the affected object
• C、Shutdown the database inNORMALmode and restart the database instance
• D、Use DBMS_META package to reconstruct the object using undo segments
• E、UseTablespacePoint in Time Recovery （TSPITR） method to recover the table and the data
• F、Use Oracle DataPumptwithflashback_timeoption toentableflashback export and then import the affected object.

第4题：

In your datawarehousing application， you generate reports frequently. The data is static in the tables being used to generate reports. You are currently using joins， resulting in a large performance overhead. What kind of database structure would you use to reduce the response time of the query？（）

• A、hash clusters
• B、index clusters
• C、partitioned tables
• D、index­organized table （IOT）

第5题：

You are a professional level SQL Server 2005 database administrator in an international corporation named Wiikigo. You are experienced in implementing high-availability solutions， monitoring the database server， and design deployment. In the company， you major job is the deployment， maintenance and support of Microsoft SQL Server 2005.You work as a database administrator for your company. You find a problem that when the following query is executed， a SQL Server 2005 application will perform slowly. SELECT * FROM Orders WHERE OrderStatus = ’InProgress’ This query is executed by the application as an ad hoc query. In most occasions， this query performs much more quickly. The company has the OrderStatus column indexed. The value InProgress is included by only a small number of the rows. Nevertheless， the OrderStatus column index which is the most ideal for this query is not being utilized. The performance of this query should be enhanced. However， the application that executes the query should not be changed. In addition， the effect on end users should be cut to the least.  Which action should be performed to finish the task？（）

• A、To finish the task， the index should be built by utilizing a FILLFACTOR of 10 percent.
• B、To finish the task， the index should be recreated to have all of the columns in the table included.
• C、To finish the task， an indexed view of the Orders table should be viewed.
• D、To finish the task， the statistics should be updated on the index.

第6题：

You are a professional level SQL Server 2005 database administrator in an international corporation named Wiikigo. You are experienced in implementing high-availability solutions， monitoring the database server， and design deployment. In the company， you major job is the deployment， maintenance and support of Microsoft SQL Server 2005. You work as a database administrator for your company. A SQL Server 2005 computer is managed by you， and a database named Customers is included by the SQL Server 2005 computer. A table named CustInfo is included by the database. An identity column named CustID and an nvarchar column named CustName are included by the table. According to the company requirement， rows which duplicate CustName values are included should be moved from the CustInfo table every year. However， the company requests to have rows removed from the CustInfo table after the rows have been manually examined and verified as being duplicates. Since you are the technical support， you are required to think out a method to have potential duplicate rows identified for manual examination. The minimum amount of administrative effort should be utilized.  Which action should be performed to finish the task？（）

• A、A trigger should be created for the CustInfo table so as to roll back INSERT queries that duplicate data is included.
• B、A new unique index should be created on the CustName column. And then， IGNORE_DUP_KEY = ON should be specified when creating index.
• C、On the CustName column， a foreign key constraint should be created， and a distinct list of CustName values is referenced by the foreign key constraint.
• D、A SELECT INTO query should be utilized， and GROUP BY and HAVING clauses should be included by the query to create a new table that contains duplicate rows from the CustInfo table.

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第13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14题：

You have many users complaining about slow inserts into a large table. While investigating the reason， you find that the number of indexes on the table is high. You want to find out which indexes are not being used.  Which method would you follow to achieve this？（）

• A、enable index monitoring and query the DBA_OBJECTS view
• B、enable index monitoring and query the DBA_INDEXES view
• C、enable index monitoring and query the V$OBJECT_USAGE view
• D、enable index monitoring and view the DBA_INDEXTYPE_COMMENTS view

第15题：

You are connecting to an Oracle database server from a client by using the following connect string：   SQL> CONNECT hr/hr@pdserver.us.oracle.com：1521/proddb   Which naming method is being used in this case？（）

• A、Local Naming
• B、Easy Connect
• C、External Naming
• D、Directory Naming

第16题：

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

第17题：

You are a professional level SQL Server 2005 database administrator in an international corporation named Wiikigo. You are experienced in implementing high-availability solutions， monitoring the database server， and design deployment. In the company， you major job is the deployment， maintenance and support of Microsoft SQL Server 2005. You work as a database administrator for your company. A SQL Server 2005 application is utilized by the company. A query is executed by the application to return three columns of the nvarchar data type and one column of the XML data type. A WHERE clause is utilized by the query， and all three of the nvarchar columns are contained by the WHERE clause. 5 million rows are included by the table， and 50，000 rows are returned by the query. The performance of the query should be enhanced. Which action should be performed to achieve the goal？（）

• A、A primary XML index should be created on the XML column.
• B、Statistics should be created on the nvarchar columns.
• C、A view should be created， and only the four columns that the query utilizes are contained by a view.
• D、A composite index should be created on the three nvarchar columns， and INCLUDE should be specified for the XML column.

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