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问题 单项选择题

将E-R图转换到关系模式时，实体与联系都可以表示成( )。

A．属性

B．关系

C．键

D．域

答案

参考答案：B

解析：数据库逻辑设计的主要工作是将E-R图转换成指定RDBMS中的关系模式。首先，从E-R图到关系模式的 转换是比较直接的，实体与联系都可以表示成关系，E-R图中属性也可以转换成关系的属性。实体集也可以转换成关系。

填空题

用不等号填空．

①若a＜b，c为任意数，则a-c______b-c

②若a＜b，c＞0，则ac______bc

③若a＜b，c＜0，则ac______bc

④若a＞b，c＜0，则a+c______b+c

其中填“＜”的题号是______，填“＞”的题号是______．
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单项选择题 共用题干题

Information systems design is defined as those tasks that focus on the specification of a detailed computer-based solution. Typically, there are four systems design tasks for in-house development. 1)The first task is to specify (1), which defines the technologies to be used by one, more, or all information systems in terms of their data, processes, interfaces, and network components. This task is accomplished by analyzing the data models and process models that are initially created during requirements analysis. 2)The next systems design task is to develop the (2). The purpose of this task is to prepare technical design specifications for a database that will be adaptable to future requirements and expansion. 3)Once the database prototype has been built, the systems designer can work closely with system users to develop input, output and dialogue specifications. The (3) must be specified to ensure that the outputs are not lost, misrouted, misused, or incomplete. 4)The fourth design task involves packaging all the specifications from the previous design tasks into a set of specifications that will guide the (4) activities during the following phases of the systems development methodology. Finally, we should (5) and update the project plan accordingly. The key deliverable should include a detailed plan for the construction phase that should follow.

空白（4）处应选择（）

A.system administrator's

B.system analyst's

C.computer programmer's

D.system designer's
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