6．设F是关系模型R的FD集，如果对F中每个非平凡函数依赖X→Y，都有X是R的超键，则R属于

A.1NF                                                              B.2NF

C.3NF                                                              D.BCNF

7．设关系R如下表，则π专业，入学年份(R)的元组数为

A.2                                                                  B.3

C.4                                                                  D.5

8．常用的关系运算是关系代数和

A.集合运算                                                      B.逻辑演算

C.关系演算                                                      D.集合演算

9．如果想找出关系R的属性A上为空的那些元组，则选择子句应该为

A.WHERE A=NULL                                          B.WHERE A==NULL

C.WHERE A IS NULL                                       D.WHERE A NOT IS NULL

10.SQL语言的聚合函数COUNT、SUM、AVG等，不允许出现在其中的子句为

A.SELECT                                                       B.HAVING

C.GROUP…HAVING                                        D.WHERE

11.下列语句中表示事务执行成功的是

A.COMMIT                                                      B.BEGIN TRANSACTION

C.ROLLBACK                                                  D.OK

12.事务把数据R的S锁升级为X锁的操作是

A.XFIND R                                                      B.SFIND R

C.UPDX R                                                       D.SRELEASE R

13.在T-SQL批处理中调用存储过程所使用的命令是

A. exec                                                            B. declare

C. user                                                             D. set

14.在PowerBuilder应用中建立窗口为w_main，下列打开此窗口的正确脚本语句是

A.open w_mam                                                 B.open(w_main)

C.display w_mam                                              D.display(w_main)

15．如果有枚举类型定义：sex{male，female}，那么male和female的值分别为

A.0，0                                                             B.0，1

C.1，0                                                             D.1，1