简述命名空间的两种引用方式。
（）的作用方向恒定，与运动方向无关。 反抗转矩。 离心式转矩。 位能转矩。 恒功率转矩。
You performed an incomplete recovery on your Oracle Database 10g database using the following command： SQL> RECOVER DATABASE 2 UNTIL TIME ’2004-08-05：12：10：03’ 3 USING BACKUP CONTROLFILE； In which situation would the above recovery be required？（） A user table was lost at the specified time.。 A redo log file was lost at the specified time.。 The backup control file is on a faster disk than the current one.。 The current control file has a different path compared with the intended time of recovery.。 The current control file does not match the physical structure of the database at the intended time of recovery.。
Examine this statement: SELECT student_id, gpa FROM student_grades WHERE gpa > &&value; You run the statement once, and when prompted you enter a value of 2.0. A report is produced. What happens when you run the statement a second time?（） An error is returned.。 You are prompted to enter a new value.。 A report is produced that matches the first report produced.。 You are asked whether you want a new value or if you want to run the report based on the previous value.。
You work as a database administrator for Certkiller .com. Your database is in NOARCHIVELOG mode. The database has been configured with three redo logs groups， and there have been five log switches. You lost one non-system-critical data file from your database. Which method would you use to recover the data file？（） Restore all the data files and open the database。 Create the data file and performtablespacerecovery。 No need to restore any file， just recover the database。 Restore only the system data file and recover the database。 Restore only lost date file and performtablespacerecovery。
曹禺一生共写下剧本（）。
