【填空题】
14. 数据模型的三要素包含数据结构、___和___
查看试卷，进入试卷练习
微信扫一扫，开始刷题
刷题
搜题
导入试题
搜题
答案
数据操作|完整性约束
解析
暂无解析
相关试题
【单选题】
一个关系中的各个元组___
A. 前后顺序不能任意颠倒，一定要按照输入的顺序排列
B. 前后顺序可以颠倒，不影响库中的数据关系
C. 前后顺序可以任意颠倒，到排列顺序不同，统计处理的结果就可能不同
D. ”前后顺序不能任意颠倒，一定要按照关键字段值的顺序排列
【单选题】
有一个关系：学生（学号，姓名，系别）规定学号的值域是8个数字组成的字符串，这一规则属于()
A. 实体完整性约束
B. 参照完整性约束
C. 用户自定义完整性约束
D. 关键字完整性约束
【单选题】
已知关系1：厂商(厂商号，厂名)，关系1的主码的为厂商号；关系2:产品(产品号，颜色，厂商号)，关系2的主码为产品号，外码为厂商号。
假设两个关系中已经存在如表2-14和表2-15所示的元组，若再往产品关系中插入如下元组：I（P03,红,C02），II(P01,蓝，C01), I I I(P04,白C04),IV(P05， 黑，null)
表2-14厂商
厂商号 厂名
C01 宏达
C02 立仁
表2-15产品
产品号 颜色 厂商号
P01 红 C01
P02 黄 C03
能够插入的元组是（）
A. I,I I,I I I
B. I,I I
C. I,II
D. I,IV
【单选题】
在关系S (NAME, SNO, DEPART)中规定DEPART属性只能是计算机。这规定属于___
A. 用户自定义完整性
B. 参照完整性
C. 实体完整性
D. 固定完整性
【单选题】
在下面的两个关系中，职工号和部门号分别为职工关系和部门关系的主码。职工(职工号，职工名，部门号，职务，工资)郁门(部门号，部门名，部门人数:工资总额)在这两个关系的属性中，只有一个属性是外码，它是___
A. 职工关系的职工号
B. 职工关系的部门号
C. 部门关系的部门号
D. 部门关系的部门名
【填空题】
3.已知“系【系编号，系名称，系主任，电话，地点】”和“学生【学号，姓名，性别，入学日期，专业，系编号】”两个关系，“系”关系的主关键字是___，“学生”关系的主关键字是___，外关键字是___
【单选题】
有关系模式“学生【学号，课程号，名次】”，若每一名学生每门课程有一定的名次，每门课程每一名次只有一名学生， 则以下叙述中错误的是___。
A. (学号，课程号)和(课程号，名次)都可以作为候选码
B. 只有(学号，课程号)能作为候选码
C. 关系模式属于第3范式
D. 关系模式属于BCNF
【单选题】
4.关系数据库规范化理论是为解决关系数据库中的___问题而引入的。
A. 插入、更新、删除和数据冗余
B. ，提高查询速度
C. 减少数据操作的复杂性
D. 保证数据的安全性和完整性
【单选题】
若关系模式R 【A, B】已属于3NF，下列说法中___是正确的。
A. 它一定消除了插入和删除异常
B. 可能存在一定的插入和删除异常
C. 一定属于BCNF
D. A和C都是
【单选题】
下列关于关系数据库规范化理论的描述中， 不正确的是___。
A. 规范化理论提供了判断关系模式优劣的理论标准
B. 规范化理论提供了判断关系数据库管理系统优劣的理论标准
C. 规范化理论对于关系数据库设计具有重要指导意义
D. 规范化理论对于其他模型的数据库的设计也有重要指导意义
【单选题】
有关系:教学【学号、教工号、课程号】，假定每个学生可以选修多门课程，每门课程可由多名学生来选修，每位教师只能讲授一门课程，每门课程只能由一位教师来讲授，那么该关系模式的主码是___。
A. 课程号
B. 教工号
C. 学号
D. 【学号，教工号】
【单选题】
下列关于关系模式规范化的叙述中，不正确的是___
A. 若R∈BCNF,则必然R∈3NF
B. 若R∈3NF,则必然R∈2NFC.
C. 若R∈2NF,则必然R∈INF
D. 若R∈INF，则必然R∈BCNF
【单选题】
下列关于E-R模型向关系模型转换的描述中，不正确的是___。
A. 一个实体类型转换成个关系模式，关系模式的码就是实体的码
B. 一个1 :n联系转换为一个关系模式，关系模式的码是1 : n联系的1端实体的码
C. 一个m: n联系转换为一一个关系模式，关系模式的码为各实体码的组合
D. 三个或三个以上实体间的多元联系转换为一个关系模式，关系模式的码为各实体码的组合
【单选题】
下列关于函数依赖的描述中，不正确的是___。
A. 若X→Y，Y→Z,则X→Z
B. 若X→Y, Y'属于Y,则X→Y'
C. 若X→Y, X'属于X,则X'→Y
D. 若X'属于X,则X →X'
【单选题】
假设有关系模式R(A.B,C,D,E),根据语义有如下函数依赖集F=｛A→C,【B,C】→D,【C,D】→A,【A,B】→E｝，则关系模式R的规范化程度最高达到___
I (A,B) II (A,D) III (B,C) IV (C,D) V (B,D)
A. 1NF
B. 2NF
C. 3NF
D. BCNF
推荐试题
【单选题】
----- "Where is your college located, John?" ----- "It is ________."___
A. on the Fifth Avenue
B. on Fifth Avenue
C. in Fifth Avenue
D. at Fifth Avenue
【单选题】
__________ is she in London than she rings up her old friend Mary.___
A. Scarcely
B. Rarely
C. No sooner
D. Hardly
【单选题】
A fireman discovered the __________ of the fire.___
A. truth
B. reason
C. cause
D. fact
【单选题】
he weather __________ us from climbing the mountain.___
A. discharged
B. disguised
C. disturbed
D. discouraged
【单选题】
I didn't expect to receive a postcard from you！It's really _____my wildest imagination.___
A. behind
B. beyond
C. except
D. through
【单选题】
She __________ in wearing that old – fashioned hat.___
A. insists
B. persists
C. assists
D. consists
【单选题】
Some of the meat came from Canada. How about________？___
A. another
B. the other
C. others
D. the rest
【单选题】
I have brought you ___ flowers for your birthday. ___
A. few
B. a few
C. little
D. a little
【单选题】
I have also experienced many adventures, but nothing that I have seen ___what you have described. ___
A. compares
B. relates
C. resembles
D. assembles
【单选题】
That young man has made so much noise that he ___ not have been allowed attend the concert. ___
A. could
B. must
C. would
D. should
【单选题】
“What is Mary doing at home?” “She is playing ____.”___
A. a piano
B. her piano
C. piano
D. the piano
【单选题】
I’m busy now ,ask him to see me ____ time.___
A. the other
B. some other
C. other
D. another
【单选题】
The child took a spoonful and tasted it carefully __________ it was hot.___
A. in case
B. provided
C. if
D. unless
【单选题】
The French pianist who had been praised very highly __________ to be a great disappointment. ___
A. turned off
B. turned up
C. turned out
D. turned down
【单选题】
“Shall I turn on the television?” – “No, I’d rather not __________ television tonight.”___
A. have watched
B. to watch
C. watch
D. for watching
【单选题】
They said that they had made up their minds to ____the task in spite of the extremely difficult conditions.___
A. carry on
B. carry off
C. carry away
D. carry forward
【单选题】
The two girls are getting on very well and share with each other. ___
A. little
B. much
C. some
D. none
【单选题】
The teacher said that the classroom was empty __________ a few chairs.___
A. but for
B. except for
C. apart from
D. besides
【单选题】
______you choose， make sure that it is a good one. ___
A. What
B. Wherever
C. Whichever
D. Which
【单选题】
Vingo was released from prison_____the successful efforts of his friends to prove his innocence. ___
A. according to
B. as a result of
C. for reasons of
D. with the help of
【单选题】
Entering the room， I found my father __ at the desk and ___ something .___
A. seat... write
B. seated ... wrote
C. seated ... writing
D. seating ... writing
【单选题】
Cake __________ of flour, sugar, egg and some other ingredients. ___
A. contained
B. consists
C. includes
D. composed
【单选题】
Mr. Peter wanted Steve to take half the money, but Steve did not __________ it. ___
A. obtain
B. achieve
C. accept
D. receive
【单选题】
I'd like to take my picture ________stands a high tower. ___
A. where
B. which
C. that
D. there
【单选题】
__________ the English examination I would have gone to the concert last Saturday. ___
A. But for
B. As for
C. In spite of
D. Because of
【单选题】
Cars moved very slowly in the 1920s, but they ______move more quickly than in 1910.___
A. were to can
B. did
C. will
D. can
【单选题】
The little girl needs __________ after her shock. ___
A. being comforted
B. be comforted
C. comforting
D. comforted
【单选题】
The __________ horse ran away from the fire.___
A. having frightened
B. frightening
C. frightened
D. frighten
【单选题】
You can take ______ seat you like. ___
A. no matter what
B. no matter which
C. what
D. whichever
【单选题】
He changed his name， _____ that nobody would find out what he had done before. ___
A. having thought
B. to think
C. thinks
D. thinking
【单选题】
----- _______is your English teacher？ ----- The one in red. ___
A. who
B. which
C. what
D. where
【单选题】
Can you give me a light for my cigarette? I have ____my matches.___
A. got out of
B. got rid of
C. got away with
D. run out of
【单选题】
Then the speaker __________ the various factors leading to the present economic crisis.___
A. went for
B. went after
C. went into
D. went on
【单选题】
I know Jonathan quite well and never doubt_____ he can do a good job of it___.
A. whether
B. that
C. when
D. what
【单选题】
I'm afraid it ______ tomorrow, but who knows?___
A. may have rained
B. might rain
C. would rain
D. ought to rain
【单选题】
He has spent ____money on his new house.___
A. a large number of
B. the number of
C. lots of
D. numbers of
【单选题】
This is the hotel __________ I like to stay.___
A. in which
B. at which
C. to which
D. at that
【单选题】
Would you mind keeping a（n）__________on the house for us while we are away？___
A. eye
B. /look
C. hand
D. view
欢迎使用我爱刷题
×
微信搜索我爱刷题小程序
温馨提示
×
请在电脑上登陆“www.woaishuati.com”使用