在教师表中，如果要找出职称为“教授”的教师，所采用的关系运算是（ ）。
A、投影
B、选择
C、联接
D、自然选择
在堆栈类SharedStack的定义中，为了保证堆栈在并发操作中数据的正确性，应在下划线处填入的修饰符是（ ）。（两个下划线的填写内容相同）public class SharedStack { ______ int idx = 0; ______ char[] data = new char[10]; public synchronized void push(char c){……} public synchronized void pop(){……}}
A、public
B、不使用修饰符
C、private
D、protected
要打开一个视图以便浏览或更新其中的数据，可以使用命令（ ）。
A、USE
B、USEVIEW
C、BROWSE
D、BROWSEVIEW
Using the LIST command in Recovery Manager (RMAN), which two pieces of information in the RMANrepository can be listed?（）
Astored scripts in the recovery catalog
Bbackups that can be deleted from disk
Cbackup sets and image copies are obsolete
Dbackups that do not have the AVAILABLE status in the RMAN repository RMAN
Matthew has recently joined NetFx Corporation as a junior-level Database Administrator （DBA）. He is asked by his supervisor to verify the database for data block corruptions. He uses the DBVERIFY utility and finds that two data blocks are corrupted in the database. What should Matthew use to identify the corrupted blocks as well as datafiles containing these blocks？（）
A、 datafile
B、 alert log
C、 dynamic views
D、 control file script
You are designing an application for a telecom company and you have been asked to design a database table to facilitate monthly bill generation. The bill would include details of customer calls， listed in chronological order. Which method would you follow to achieve this objective without increasing the overhead of sorting the rows？（）
A、create a hash cluster to store the data
B、create an index cluster to store the data
C、create a partitioned table to store the data
D、create a sorted hash cluster to store the data
E、create a heap table with rowid to store the data