多选题Examine this command: SQL exec DBMS_STATS.SET_TABLE_PREFS (‘SH’, ‘CUSTOMERS’, ‘PUBLISH’, ‘false’); Which three statements are true about the effect of this command?（）AStatistics collection is not done for the CUSTOMERS table when schema stats are gath

第1题：

第2题：

You are working in an online transaction processing (OLTP) environment. You use the FLASHBACKTABLE command to flash back the CUSTOMERS table. Before executing the FLASHBACK TABLE command, the system change number (SCN) was 663571. After flashing back the CUSTOMERS table, you realize that the table is not in the correct state. Now, you need to reverse the effects of the FLASHBACK TABLE command. Which is the fastest and the most efficient option to reverse the effects of the FLASHBACK TABLE command?（）

• A、Restore the backup control file and open the database with RESETLOGS option.
• B、Perform point-in-time recovery because flashback cannot be performed again on this table
• C、Execute the FLASHBACK DATABASE statement to retrieve the CUSTOMERS table as it was at SCN 663571
• D、Execute another FLASHBACK TABLE statement to retrieve the CUSTOMERS table as it was at SCN 663571

第3题：

第4题：

You want to capture column group usage and gather extended statistics for better cardinality estimates for the CUSTOMERS table in the SH schema. Examine the following steps: 1. Issue the SELECT DBMS_STATS.CREATE_EXTENDED_STATS (‘SH’, ‘CUSTOMERS’) FROM dual statement. 2. Execute the DBMS_STATS.SEED_COL_USAGE (null, ‘SH’, 500) procedure. 3. Execute the required queries on the CUSTOMERS table. 4. Issue the SELECT DBMS_STATS.REPORT_COL_USAGE (‘SH’, ‘CUSTOMERS’) FROM dual statement. Identify the correct sequence of steps.（）

• A、3，2，1，4
• B、2，3，4，1
• C、4，1，3，2
• D、3，2，4，1

第5题：

Examine the command that is used to create a table：  SQL> CREATE TABLE orders（oid NUMBER（6） PRIMARY KEY， odate DATE， ccode NUMBER（6）， oamt NUMBER（10，2）） TABLESPACE users；  Which two statements are true about the effect of the above command） （）

• A、A CHECK constraint is created on the OID column.
• B、A NOT NULL constraint is created on the OID column.
• C、The ORDERS table is the only object created in the USERS tablespace.
• D、The ORDERS table and a unique index are created in the USERS tablespace.
• E、The ORDERS table is created in the USERS tablespace and a unique index is created on the OIDcolumn in the SYSTEM tablespace.

第6题：

Examine the command： SQL> DBMS_STATS.SET_TABLE_PREFS（’SH’， ’CUSTOMERS’， ’PUBLISH’， ’false’）；  Which statementdescribes the effect of the above command（）

• A、Automatic statistics collection is stopped for the CUSTOMERS table.
• B、Statistics for the CUSTOMERS table are locked and cannot be overwritten.
• C、Existing statistics for the CUSTOMERS table become unusable for the query optimizer.
• D、Subsequently， statistics gathered on the CUSTOMERS table are stored as pending statistics

第7题：

You execute this command to drop the ITEM table， which has the primary key referred in the ORDERtable：  SQL> DROP TABLE scott.item CASCADE CONSTRAINTS PURGE；  Which two statements are true about the effect of the command（）

• A、No flashback is possible to bring back the ITEM table.
• B、The ORDER table is dropped along with the ITEM table.
• C、The dependent referential integrity constraints in the ORDER table are disabled.
• D、The dependent referential integrity constraints in the ORDER table are removed.
• E、The table definition of the ITEM table and associated indexes are placed in the recycle bin.

第8题：

第9题：

You execute the following command in your Certkiller .com production database to change the width of the CUST_NAME column of the CUSTOMERS table： ALTER TABLE customers  MODIFY （cust_nameVARCHAR2 （40）） /  When you execute the command， it displays the following error message：  ERROR at line 1：  ORA-00054： resource busy and acquire with NOWAIT specified  What could be the reason for the error message？（）

• A、The database instance is not available.
• B、The ALTER TABLE command does not have WAIT option
• C、The table or a row in the table is currently locked by another user session.
• D、The database instance is busy processing other user sessions commands.
• E、The CUSTOMERS table has no long running query active at the time when this request is made.
• F、The server process executing the ALTER TABLE command is busy with another command execution

第10题：

You executed the following commands：   SQL> ALTER SESSION SET OPTIMIZER_USE_PENDING_STATISTICS = false； SQL> EXECUTE DBMS_STATS.SET_TABLE_PREFS（’SH’， ’CUSTOMERS’， ’PUBLISH’，’false’）； SQL> EXECUTE DBMS_STATS.GATHER_TABLE_STATS（’SH’， ’CUSTOMERS’）；   Which statement is correct regarding the above statistics collection on the SH.CUSTOMERS table in the above session？（）

• A、 The statistics are stored in the pending statistics table in the data dictionary.
• B、 The statistics are treated as the current statistics by the optimizer for all sessions.
• C、 The statistics are treated as the current statistics by the optimizer for the current sessions only.
• D、 The statistics are temporary and used by the optimizer for all sessions until this session terminates.