数据库代写 | IS5413 Database Management Systems

数据库管理系统(DBMS)是一个软件包,旨在定义、操作、检索和管理数据库中的数据。一个DBMS通常操作数据本身、数据格式、字段名、记录结构和文件结构。它还定义了验证和操作这些数据的规则。

随着管理数据库的实践的发展,数据库管理系统是建立在特定的数据处理概念上的。最早的数据库只处理个别单一的特殊格式的数据。今天更进化的系统可以处理不同种类的不太格式化的数据,并以更复杂的方式将它们绑在一起。

随着时间的推移,数据库管理系统的模式已经发生了很大的变化。这是理解各种DBMS选项如何工作的关键部分。

最早的数据库管理系统类型主要包括层次结构和网络模型。

层次模型是指每个节点或组件与其他一个节点或组件有一个子/父关系。在网络模型中,区别在于一个组件可以有多种关系–可以认为这是一个单一的节点能够 “多播 “连接。然而,随着时间的推移,这些模型被称为关系型数据库的东西所取代。在关系数据库模型中,单个组件有属性,这些属性通过数据库表设计与它们的身份相联系。一个单独的数据库表的行和列包括这些身份和属性,以这种方式,传统的结构化查询语言或SQL可以用来在这些关系模型上提取各种信息。

从那时起,出现了一个甚至更新的概念,叫做NoSQL。专家建议,理解NoSQL的最佳方式是将其翻译为 “不仅仅是SQL”,或者换句话说,广泛使用NoSQL来描述超越传统SQL和关系型数据库模型的系统。NoSQL数据库设计的一些考虑涉及数据的规范化或结构化程度,以及数据库系统如何处理。工程师们还必须关注整个系统中数据的一致性和分辨率的工具,以促进统一性和修复各种相关问题。

其他类型的DBMS模型包括图形数据库模型,其中图形模型被用于语义查询,以及实体关系模型。这些都为传统的关系型数据库设计提供了进一步的选择。一些最新类型的DBMS可以用于数据中心可能有不同格式或相对无格式或 “原始 “数据的广泛差异的地方,这些地方的记录没有以传统的方式进行规范。这和其他类型的进步使DBMS的世界变得更加复杂,并提高了经验丰富的DB工程师和管理员对现代系统的价值。

下面是一个数据库系统代考的高分通过案例:

Question 1:

a) Why would a company choose not to implement all its tables in 3NF, but leave

some in 1NF or 2NF instead? Explain with an example.

b) A database is designed to help companies achieve central storage of data so as

to reduce data redundancy and improve data consistency. Why do companies

still create multiple databases?

c) What are the reasons for creating views using SQL? Explain how a view can be

used to reinforce data security?

d) List five potential benefits of the database approach compared to the

conventional file system approach.

e) Cloud computing is gaining wide acceptance in industry. It involves sharing hardware (e.g. IaaS: Infrastructure as a Service), system software (e.g., PaaS:Platform as a Service) and application software (e.g. SaaS: Software as a Service) on the cloud so as to create a win-win situation (an example of a shared economy) for both customers and software vendors. Please explain how Client/Server database architecture can fit into the cloud computing framework.

Question 2:

An Internet bank wishes to expand its business in the credit card area. Currently it supports customers with two types of card accounts: debit cards and credit cards. Credit card accounts accumulate charges with merchants. Each charge is about 3% of the transaction amount and is identified by the date and amount of the charge. A detailed EER diagram for its business expansion is shown in the figure below:

Answer the following questions (Note any unspecified requirements and make appropriate assumptions to make the specification complete).

a) Convert the above EER diagram into the relational schema.

b) Show all the functional dependencies that should hold among the attributes.

c) Design relation schemas for the database in 3NF. Specify the primary and foreign key attributes of each relation.

Question 3:

Consider the following database for class scheduling with sample values:

Write SQL statements for the following queries:

a) How many students are enrolled in Section 2714 in the first semester of 2006 (I-2006) ?

b) Which faculty members are qualified to teach a course since 1995? List the

faculty ID, course, and date of qualification.

c) List the students who are enrolled in each course in Semester I, 2006 (I-2006).

Group the students by the sections in which they are enrolled.

d) Is any instructor qualified to teach ISM 3113 and not qualified to teach ISM

4930.

e) How many students are enrolled in section 2714 during semester I-2006.

f) Which students were not enrolled in any courses during semester I-2006?

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