首页
登录
从业资格
When we talk about a database, we must d
When we talk about a database, we must d
admin
2022-08-02
53
问题
When we talk about a database, we must differentiate between the database (1),which is the logical design of the database, and the database (2), which is a snapshot of the data in the database at a given instant in time. The concept of a relation corresponds to the programming-language notion of a variable, while the concept of a relation schema corresponds to the programming-language notion of type definition. In general, a relation schema consists of a list of(3)and their corresponding domains. The concept of a relation instance corresponds to the programming-language notion of a value of a (4) . The value of a given variable may change with time; similarly the contents of a relation instance may change with time as the relation is updated. In contrast, the (5) Of a relation does not generally change.问题1 A.schema B.instance C.table D.entity问题2 A.schema B.table C.instance D.entity问题3 A.variable B.attributes C.rows D.notions问题4 A.constant B.variable C.struct D.array问题5 A.table B.schema C.instance D.view
选项
答案
ACBBB
解析
第1空和2空:当我们谈论数据库时,我们必须区分数据库模式(它是数据库的逻辑设计)和数据库实例(它是给定时刻数据库中数据的快照)。
第3空:一般来说,关系模式由属性列表以及相应的域组成。比如R(A1,A2,…An)。
第4空:关系实例的概念对应于编程语言中变量值的概念。
第5空:类似地,关系实例的内容可能会随着时间的推移而变化,因为关系会被更新。相反,关系的模式通常不会改变。
转载请注明原文地址:https://tihaiku.com/congyezige/2420118.html
本试题收录于:
中级 数据库系统工程师题库软件水平考试初中高级分类
中级 数据库系统工程师
软件水平考试初中高级
相关试题推荐
The()schemeinadatabasesystemisre
()ofdatabasereferstotheprotectio
Whenwetalkaboutadatabase,wemustd
Adatabasesystemisacollectionofint
ADatabaseManagementSystem(DBMS)consis
随机试题
[originaltext]Q:Hello.Isthisyourmanager’soffice?[/originaltext][original
BreakoutoftheeverydayroutineandcomealiveagainwithatriptoFlorida
There’saschooloflinguisticsthatbelieveslanguagelearningbeginswith
QuickChangeinStrategyforaBooksellerInthemovieY
如图17所示正方形截面杆,力F作用线通过截面形心C,则该杆发生()。A平面弯
学生的群体差异主要指的是()。A.年龄 B.学习方式 C.性格 D.社会
某男,63岁。胸部闷痛半年,有时胸痛彻背,冬季频发且症状加重,平时常有心悸怔忡,
以下哪项是记忆障碍在脑器质性精神障碍的早期主要表现() A.错构 B.虚构
按信息的内容属性,建设工程项目的信息可以分为()。A.设计准备信息、设计信息、
下列成本管理措施中,属于合同措施的是()。A.编制成本计划 B.对不同的技术
最新回复
(
0
)