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请说明操作系统作业管理的功能?作业调度算法是指按照什么样的原则来选取作业并投入运行?调度算法的合理性直接影响系统的效率,作业调度算法有哪些?对算法的选择需要考虑哪些问题?

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黑客 ()传输控制/因特网协议

按规范设计的方法将数据库设计分为六个阶段:(1)需求分析。(2)概念结构设计。 (3)逻辑结构设计。(4)数据库物理设计。(5)数据库实施。(6)数据库运行和维护。
针对关系数据库设计的逻辑结构设计,回答下述问题:
1.逻辑设计的目的。
2.逻辑设计过程中,如何将E-R模型向关系数据模型转换?
3.关系数据库逻辑设计的步骤和内容。

PART 3
Discussion topics:
★Developments in education
How has education changed in your country in the last 10 years?
What changes do you foresee in the next 50 years?
★A national education system
How do the expectations of today's school leavers compare with those of the previous generation?
What role do you think extracurricular activities play in education?
★Different styles/methods of teaching and learning
What method of learning works best for you?
How beneficial do you think it is to group students according to their level of ability?

在sQL语言中,如果要对一个基本表增加列和完整性约束条件,应该使用SQL语言的一【 】语句。

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