6．設(shè)F是關(guān)系模型R的FD集，如果對F中每個非平凡函數(shù)依賴X→Y，都有X是R的超鍵，則R屬于

A.1NF                                                              B.2NF

C.3NF                                                              D.BCNF

7．設(shè)關(guān)系R如下表，則π_{專業(yè)，入學(xué)年份}(R)的元組數(shù)為

A.2                                                                  B.3

C.4                                                                  D.5

8．常用的關(guān)系運算是關(guān)系代數(shù)和

A.集合運算                                                      B.邏輯演算

C.關(guān)系演算                                                      D.集合演算

9．如果想找出關(guān)系R的屬性A上為空的那些元組，則選擇子句應(yīng)該為

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

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

10.SQL語言的聚合函數(shù)COUNT、SUM、AVG等，不允許出現(xiàn)在其中的子句為

A.SELECT                                                       B.HAVING

C.GROUP…HAVING                                        D.WHERE

11.下列語句中表示事務(wù)執(zhí)行成功的是

A.COMMIT                                                      B.BEGIN TRANSACTION

C.ROLLBACK                                                  D.OK

12.事務(wù)把數(shù)據(jù)R的S鎖升級為X鎖的操作是

A.XFIND R                                                      B.SFIND R

C.UPDX R                                                       D.SRELEASE R

13.在T-SQL批處理中調(diào)用存儲過程所使用的命令是

A. exec                                                            B. declare

C. user                                                             D. set

14.在PowerBuilder應(yīng)用中建立窗口為w_main，下列打開此窗口的正確腳本語句是

A.open w_mam                                                 B.open(w_main)

C.display w_mam                                              D.display(w_main)

15．如果有枚舉類型定義：sex{male，female}，那么male和female的值分別為

A.0，0                                                             B.0，1

C.1，0                                                             D.1，1