Bài Tập Cơ Sở Dữ Liệu

Họ và tên: Trịnh Thanh Quân, SV Học viện Ngân hàng
Lớp:
Bài làm:
Câu 1: Define each of the following terms:
a. data
b. field
c. record
d. file
a) Data: In computing, data is information that has been translated into a form that is
efficient for movement or processing.
b) Field: A division of a database (= a collection of similar information on a computer)
that contains a particular type of information, such as names or numbers.
c) Record: to store sounds or moving pictures using electronic equipment so that they can
be heard or seen later:
d) File: any of several different types of container used to store papers, letters, and other
documents in an ordered way, especially in an office.
Câu 2: What is data redundancy, and which characteristics of the file system can
lead to it?
Data redundancy occurs when the same piece of data exists in multiple places, whereas
data inconsistency is when the same data exists in different formats in multiple tables.
Unfortunately, data redundancy can cause data inconsistency, which can provide a
company with unreliable and/or meaningless information.
The use of spreadsheets and tables in different parts of the organization can cause it.
Câu 3: What is data independence, and why is it lacking in file systems?
Data independence is changing the data storage characteristics without affecting the
program’s ability to access the data. It lacks in file systems because it holds no practical
significance to the logical data format or the physical data format.
Data independence is the ability of to make changes to data characteristics without have
to make changes to the programs that access the data. It’s important because of the
savings in time and potential errors caused by reducing modifications to data access
software.

Câu 4: What is a DBMS, and what are its functions?
Database Management Systems (DBMS) are software systems used to store, retrieve, and
run queries on data. A DBMS serves as an interface between an end-user and a database,
allowing users to create, read, update, and delete data in the database.
DBMS manage the data, the database engine, and the database schema, allowing for data
to be manipulated or extracted by users and other programs. This helps provide data
security, data integrity, concurrency, and uniform data administration procedures.
Câu 5: What is structural independence, and why is it important?
Structural independence exists when you can change the file structure without affecting
the application's ability to access the data.
It matters because if it doesn't exist (or is structural dependent) any change to a file's
structure (i.e. adding a new field) would require a program to read a record from the
original file transform the original data to conform to the new structure's storage
requirements write the transformed data into the new file structure and repeat the steps
for EVERY single record in the file.
Câu 6: Explain the differences among data, information, and a database.
Generally We can speak in a very simplified way:
+) Information is knowledge about some facts, and it can be either structured or nonstructed.
+) Data is information in structured form.
+) Database is a piece of software that manages a physical storage where structured
information may be stored in a way that enables transactional control. Concurrent
access, provides for data consistency, data seccurity etc.
Câu 7: What is the role of a DBMS, and what are its advantages? What are its
disadvantages?
DBMS manage the data, the database engine, and the database schema, allowing
for data to be manipulated or extracted by users and other programs. This helps
provide data security, data integrity, concurrency, and uniform data administration
procedures.

Advantages of Database Management System (DBMS)


1. Improved data sharing
An advantage of the database management approach is, the DBMS helps to create an
environment in which end users have better access to more and better-managed
data..Such access makes it possible for end users to respond quickly to changes in their
environment.
2. Improved data security
The more users access the data, the greater the risks of data security breaches.
Corporations invest considerable amounts of time, effort, and money to ensure that
corporate data are used properly. A DBMS provides a framework for better enforcement
of data privacy and security policies.
3. Better data integration
Wider access to well-managed data promotes an integrated view of the organization’s
operations and a clearer view of the big picture. It becomes much easier to see how
actions in one segment of the company affect other segments.
4. Minimized data inconsistency
Data inconsistency exists when different versions of the same data appear in different
places. For example, data inconsistency exists when a company’s sales department stores
a sales representative’s name as “Bill Brown” and the company’s personnel department
stores that same person’s name as “William G. Brown,” or when the company’s regional
sales office shows the price of a product as $45.95 and its national sales office shows the
same product’s price as $43.95. The probability of data inconsistency is greatly reduced
in a properly designed database.
5. Improved data access
The DBMS makes it possible to produce quick answers to ad hoc queries. From a
database perspective, a query is a specific request issued to the DBMS for data
manipulation—for example, to read or update the data. Simply put, a query is a question,
and an ad hoc query is a spur-of-the-moment question. The DBMS sends back an answer

(called the query result set) to the application. For example, end users, when dealing with
large amounts of sales data, might want quick answers to questions (ad hoc queries) such
as:
- What was the dollar volume of sales by product during the past six months?
- What is the sales bonus figure for each of our salespeople during the past three
months?
- How many of our customers have credit balances of 3,000 or more?


6. Improved decision making
Better-managed data and improved data access make it possible to generate betterquality information, on which better decisions are based. The quality of the information
generated depends on the quality of the underlying data. Data quality is a comprehensive
approach to promoting the accuracy, validity, and timeliness of the data. While the
DBMS does not guarantee data quality, it provides a framework to facilitate data quality
initiatives.
7. Increased end-user productivity
The availability of data, combined with the tools that transform data into usable
information, empowers end users to make quick, informed decisions that can make the
difference between success and failure in the global economy.
Till now we have seen different benefits of database management systems. But it has
certain limitations or disadvantages.
Disadvantages of Database Management System (DBMS):
Although the database system yields considerable advantages over previous data
management approaches, database systems do carry significant disadvantages. For
example:
1. Increased costs
one of the disadvantages of dbms is Database systems require sophisticated hardware
and software and highly skilled personnel. The cost of maintaining the hardware,
software, and personnel required to operate and manage a database system can be
substantial. Training, licensing, and regulation compliance costs are often overlooked

when database systems are implemented.
2. Management complexity
Database systems interface with many different technologies and have a significant
impact on a company’s resources and culture. The changes introduced by the adoption of
a database system must be properly managed to ensure that they help advance the
company’s objectives. Given the fact that database systems hold crucial company data
that are accessed from multiple sources, security issues must be assessed constantly.
3. Maintaining currencency
To maximize the efficiency of the database system, you must keep your system
current. Therefore, you must perform frequent updates and apply the latest patches and
security measures to all components.


Because database technology advances rapidly, personnel training costs tend to be
significant. Vendor dependence. Given the heavy investment in technology and personnel
training, companies might be reluctant to change database vendors.
As a consequence, vendors are less likely to offer pricing point advantages to existing
customers, and those customers might be limited in their choice of database system
components.
4. Frequent upgrade/replacement cycles
DBMS vendors frequently upgrade their products by adding new functionality. Such
new features often come bundled in new upgrade versions of the software. Some of these
versions require hardware upgrades. Not only do the upgrades themselves cost money,
but it also costs money to train database users and administrators to properly use and
manage the new features.
Câu 8: List and describe the different types of databases.
In many cases, individuals find that they need different kinds of databases for different
tasks. Below are some common types of databases:

Centralized database

Cloud database
Commercial database
Distributed database
End-user database
Graph database
NoSQL database
Object-oriented database
Open-source database
Operational database
Personal database
Relational database
Centralized database


A centralized database is one that operates entirely within a single location.
Centralized databases are typically used by bigger organizations, such as a business or
university. The database itself is located on a central computer or database system. Users
can access the database through a computer network, but it is the central computer that
runs and maintains the database.

Cloud database
A cloud database is one that runs over the Internet. The data is stored on a local hard
drive or server, but the information is available online. This makes it easy to access your
files from anywhere, as long as you have an Internet connection. To use a cloud database,
users can either build one themselves or pay for a service to store their data for them.
Encryption is an essential part of any cloud database, as all information needs to be
protected as it is transmitted online.

Commercial database
A commercial database is any that is designed by a commercial business. Businesses

develop feature-rich databases, which they then sell to their customers. Commercial
databases can vary in terms of composition or the technology they use. The defining trait
of commercial databases is having users pay to use them, unlike open source databases.

Distributed database
A distributed database is one that is spread out over multiple devices. Rather than
having all information stored on a single device, like other databases on this list,
distributed databases will operate across multiple machines, such as different computers
within the same location or across a network. The benefits of a distributed database
include increased speed, better reliability and ease of expansion.
End-user database
End-user is a term used in product development that refers to the person who uses the
product. An end-user database is, therefore, a database that is primarily used by a single
person. A good example of this type of database is a spreadsheet stored on your local
computer.

Graph database


Graph databases are databases that focus equally on the data and the connections
between them. In this database, data is not constricted to predefined models. Most other
databases can find connections between data when you run a search. With a graph
database, these connections are stored inside the database right alongside the original
data. This makes for a more efficient and faster database when your primary goal is to
manage the connections between your data.

NoSQL database
A NoSQL database has a hierarchy similar to a file folder system and the data within it
is unstructured, or non-relational. This lack of structure allows them to process larger
amounts of data at speed and makes it easier to expand in the future. Cloud computing

regularly makes use of NoSQL databases.

Object-oriented database
Object-oriented databases are ones in which data is represented as objects and
classes. An object is an item, such as a name or phone number, while a class is a group
of objects. Object-oriented databases are a type of relational database. Consider using an
object-oriented database when you have a large amount of complex data that you want to
process quickly.

Open-source database
An open-source database is designed for the public to use for free. Unlike
commercial databases, users can download or sign up for open source databases without
paying a fee. The term "open source" refers to a program in which users can see how it was
written and constructed and are free to make their own changes to the program. Opensource databases are typically much cheaper than commercial databases, but they can also
lack some of the more advanced features found in commercial databases.

Operational database
The purpose of an operational database is to allow users to modify data in real
time. Operational databases are critical in business analytics and data warehousing. They
can be set up either as relational databases or NoSQL, depending on needs.
Conventional databases rely on batch processing, where commands are carried out in


groups. Operational databases, on the other hand, allow you to add, edit and remove data
at any moment.
Personal database
A personal database is one that is designed for a single person. It is typically stored
on a personal computer and has a very simple design, consisting of only a few tables.
Personal databases are not typically suitable for complex operations, large amounts of
data or business operations.

Relational database
Relational databases are the other major type of database, opposite of NoSQL. With a
relational database, information is stored structured about other data. A good
representation of a relational database would be the connection between a person shopping
online and their shopping cart. Relational databases are often preferred when you are
concerned about the integrity of your data, or when you're not particularly focused on
scalability.
Câu 9: What are the main components of a database system?
The five major components of a database are hardware, software, data, procedure, and
database access language.
Câu 10: What is metadata?
Metadata is "data that provides information about other data" but not the content of
the data, such as the text of a message or the image itself. There are many distinct types of
metadata, including:
Descriptive metadata – the descriptive information about a resource. It is used for
discovery and identification. It includes elements such as title, abstract, author, and
keywords.
Structural metadata – metadata about containers of data and indicates how
compound objects are put together, for example, how pages are ordered to form chapters.
It describes the types, versions, relationships, and other characteristics of digital materials.
Administrative metadata – the information to help manage a resource, like resource
type, permissions, and when and how it was created.
Reference metadata – the information about the contents and quality of statistical
data.
Statistical metadata, also called process data, may describe processes that collect,
process, or produce statistical data.


Legal metadata – provides information about the creator, copyright holder, and
public licensing, if provided.

Metadata is not strictly bounded to one of these categories, as it can describe a
piece of data in many other ways.
Câu 11: Explain why database design is important.
A good database design is, therefore, one that:
+) Divides your information into subject-based tables to reduce redundant data.
+) Provides Access with the information it requires to join the information in the
tables together as needed.
+) Helps support and ensure the accuracy and integrity of your information.
Accommodates your data processing and reporting needs.
Câu 12: What are the potential costs of implementing a database system?
The potential costs of implementing a database system could include:
+)sophisticated hardware and software, trained personnel
+)training, licensingm and regulation compliance costs
+)vendor dependence - vendors are less likely to offer pricing point advantages to
existing customers
+)updating of hardware and software; additional training
Câu 13: Use examples to compare and contrast unstructured and structured
data. Which type is more prevalent in a typical business environment?
Unstructured data is simply data that has not been processed to yield information.
examples of both types would include:

An invoice. If one were to take an invoice and simply scan it into a graphic, it
would be unstructured data. In contrast, if it were processed and put into a database
(subsequently becomming structured data), employees could eventually find the monthly
averages, amount owed, etc. from various invoices.


While both are prevelant, I would think semistructed data would be the most
common in a typical business. Some data is stored but not processed (unstructured data
such as memos), and some others are stored in databases (such as invoices) but most data

are only processed to a certain extent that is displayed in a prearranged format but not able
to yield all of the information contained within.
Câu 14: What are some basic database functions that a spreadsheet cannot perform?
spreadsheets do not support basic functionality such as:
+) support for self-documentation through metadata
+)Enforcement of data types or domains to ensure consistency of data within a column,
defined relationships among tables, or contraints to ensure consistency of data across
related tables.
end

Câu 15: What common problems do a collection of spreadsheets created by
users share with the typical file system?

Common problems with using both a collection of spreadsheets created by end
users and the typical file system include:
+)lengthy development times
+) difficulty of getting quick answers
+) complex system administration
+) lack of security and limited data sharing
+)extensive programming
Câu 16: Explain the significance of the loss of direct, hands-on access to
business data that end users experienced with the advent of computerized data
repositories.
The loss of direct, hands on access to business data to end-users was significant
because it gave them the tools to convert their data into the information they needed and
manipulating the company data that would allow them to create new information.


However, it seperated end-users from data. While this increased security,
prevented redundancy and the such, it also created a delay in which the end-user could

request information from the data and when it was delivered by the DP.
Câu 17: Explain why the cost of ownership may be lower with a cloud
database than with a traditional, company database
Cloud database eliminates the need for establishing and maintaining data centres.
Explanation:Cloud computing provides an organisation with the infrastructure
they need but can not afford. A large online storage with access control policies is
available based to subscription.
For a company to establish a data centre, they would need a team of skilled
network engineers, fleet of high speed server systems and large storage devices.
The daily power supply and management, coupled with the needed skills and items,
can be overwhelming for a company whose main objective is not to deliver database
services. So cloud computing is adopted to reduce the cost.