Database Management Systems - sabraz · 11/1/2017 · MIT 22033 Database Management Systems Lesson 01: Introduction By S. Sabraz Nawaz Senior Lecturer in MIT, FMC, SEUSL

MIT 22033

Database Management Systems

Lesson 01: Introduction

By

S. Sabraz Nawaz

Senior Lecturer in MIT, FMC, SEUSL

Learning Outcomes

• At the end of the module the student will be able to:

• ▪ Describe the fundamental concepts in databases and data processing

• ▪Analyze and systematically represent relationships in data records and perform data

• modeling Create, populate and manage relational databases in desktop and server

• environments

• ▪ Use query languages to populate, update and retrieve data from databases

• ▪ Implement basic security in database systems Outline Syllabus

• ▪An introduction to data processing and databases Database management systems Data

• analysis and Data modeling (ER diagrams and conceptual modeling)

• ▪ Relational models and normalizations

• ▪ Creating databases using GUI tools Query Languages (Standard Query language)

• Introduction to database security

MIT 22033, Database Management

Systems By: S.Sabraz Nawaz2

Outline Syllabus

• 1. Introduction to DBMS.

• 2. Database model& Scheme

• 3. Data Base Design ER model

• 4. Structure Query Language

• 5. Table normalization

• 6. Security concepts & introducing advanced database

concepts



Introduction

• A database management system (DBMS) is a software package designed to create and maintain databases

(examples?)

4MIT 22033, Database Management

Systems By: S.Sabraz Nawaz

Introducing the Database

• What is a database? A database is a collection of related data

(University Database, Credit Card Processing Systems, Airline

Reservation Systems, Banking System, etc.)

• A database is a shared, integrated computer structure that

stores a collection of: End-user data, that is, raw facts of

interest to the end user.

• Efficient data management typically requires the use of a

computer database.

• Metadata, or data about data, through which the end-user data

are integrated and managed.



Database Management System

(DBMS)

• A is a collection of programs that manages the database

structure and controls access to the data stored in the database.

In a sense, a database resembles a very well-organized

electronic filing cabinet in which powerful software, known as

a database management system, helps manage the cabinet’s

contents.



DBMS: Role and Advantages

• The DBMS serves as the intermediary between the user and

the database. The database structure itself is stored as a

collection of files, and the only way to access the data in those

files is through the DBMS.



DBMS: Role



DBMS: Role…

• The DBMS receives all application requests and translates

them into the complex operations required to fulfill those

requests. The DBMS hides much of the database’s internal

complexity from the application programs and users.

• The application program might be written by a programmer

using a programming language such as Visual Basic.NET,

Java, or C#, or it might be created through a DBMS utility

program.



DBMS: Advantages

• Having a DBMS between the end user’s applications and the

database offers some important advantages.

o First, the DBMS enables the data in the database to be shared among

multiple applications or users.

o Second, the DBMS integrates the many different users’ views of the

data into a single all-encompassing data repository.



DBMS: Advantages - Improved

data sharing• The DBMS helps 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

• Concurrent accesses are scheduled by DBMS: users can think

of the data as being accessed by one user at a time




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.



DBMS: Advantages - 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.



DBMS: Advantages -

Minimized data inconsistency• Data inconsistency exists when different versions of the same

data appear in different places.

• The probability of data inconsistency is greatly reduced in a

properly designed database.




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 an

unpremeditated question. The DBMS sends back an answer

(called the query result set) to the application.

• Example?




decision making• Better-managed data and improved data access make it

possible to generate better-quality 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.



DBMS: Advantages - 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.



DBMS: Advantages- Reduced

Application Development Time

• DBMS supports many functions common to applications that

access the database

• These applications are likely to be more robust than

applications developed from scratch because many important

tasks are handled by DBMS instead of being implemented by

the application

• Note: The advantages of using a DBMS are not limited to the

few just listed. In fact, you will discover many more

advantages as you learn more about the technical details of

databases and their proper design.



Types of Databases

• A DBMS can support many different types of databases.

Databases can be classified according to the number of users,

the database location(s), and the expected type and extent of

use.



Types of Databases: Number of

Users • A single-user database supports only one user at a time. In

other words, if user A is using the database, users B and C must wait until user A is done. A single-user database that runs on a personal computer is called a desktop database.

• A multiuser database supports multiple users at the same time. When the multiuser database supports a relatively small number of users (usually fewer than 50) or a specific department within an organization, it is called a workgroup database.

• When the database is used by the entire organization and supports many users (more than 50, usually hundreds) across many departments, the database is known as an enterprise database.



Types of Databases: Location

• A database that supports data located at a single site is

called a centralized database.

• A database that supports data distributed across

several different sites is called a distributed

database.



Types of Databases: Time and

Usage• Based on how DBMS are used and on the time sensitivity of

the information gathered from them:

o Operational Database (Transactional or production

database)

o Data warehouse




Usage Operational Database• Transactions such as product or service sales, payments, and

supply purchases reflect critical day-to-day operations. Such

transactions must be recorded accurately and immediately

• A database that is designed primarily to support a company’s

day-to-day operations is classified as an operational database

(sometimes referred to as a transactional or production

database).




Usage data warehouse • A data warehouse focuses primarily on storing data used to

generate information required to make tactical or strategic decisions. Such decisions typically require extensive “data massaging” (data manipulation) to extract information to formulate pricing decisions, sales forecasts, market positioning, and so on.

• Most decision support data are based on data obtained from operational databases over time and stored in data warehouses. Additionally, the data warehouse can store data derived from many sources. To make it easier to retrieve such data, the data warehouse structure is quite different from that of an operational or transactional database.



Example of a database:

University DB

• University database maintaining information

concerning:

o Students

o Courses, and

oGrades

o…



26

An example of a database that stores students and their grades of followed courses

STUDENT Name StudentNumber Class Major

Smith 17 1 CS

Brown 8 2 CS

COURSE CourseName CourseNumber CreditHouse Department

Intro to Computer Science CS 1310 4 CS

Data Structures CS 3320 4 CS

Discrete Mathematics MATH 2410 3 MATH

Database CS 3380 3 CS

SECTION Sectionaldentifier CourseNumber Semester Year Instructor

85 MATH 2410 Fall 98 King

92 CS 1310 Fall 98 Anderson

102 CS 3320 Spring 99 Knuth

112 MATH 2410 Fall 99 Chang

119 CS 1310 Fall 99 Anderson

135 CS 3380 Fall 99 Stone

GRADE_REPORT StudentNumber Sectionaldentifier Grade

17 112 B

17 119 C

8 85 A

8 92 A

8 102 B

8 135 A



Example: University DB (cont…)

• It shows the database structure and a few sample data.

• It is organized as five files.

o The STUDENT file – data on each student,

o The COURSE file – data on each course,

o The SECTION file – data on each section of a course,

o The GRADE_REPORT file – data on grades that students

receive in the various sections they have completed, and

o The PREREQUISITE file – data on prerequisite of each course.



Need for a DBMS

❖ Traditional File System provided by the Operating System is

insufficient to meet the requirements of enterprise applications

Scenario:

A company has a large collection (500 GB) of data on database.

This data is accessed concurrently by several employees.

Questions about the data must be answered quickly, changes

made to the data by different users must be applied

consistently, and access to certain parts of the data must be

restricted.



When NOT to use a DBMS

• High initial investment (DBMS is an expensive software package)

• Applications use small amounts of data

• Lack of resources (disk space, memory, etc.) to support a database

• Single-user applications

• Overhead for flexible querying, security, concurrent access & crash recovery is not required



Describing & Storing Data in a

DBMS• A data model is a collection of high-level data description

constructs used to model the application domain

• Data model hides the low-level storage details

• Most commercial database systems are based on the

relational data model

• It is easier to use a semantic data model to model an

application domain. A well-known semantic data model is

the Entity Relationship (ER) Model




DBMS (cont.…)• In relational data model, the main construct is a relation.

• A relation has fields that belong to it which contain the name & data type of each field

• A description of data in terms of a data model is called the schema.

o Every relation has a schema, which describes the name of the relation, name of each attribute (field or column), and the type of each column.

o e.g. Students(sid: string, name: string, login: string,

age: integer, gpa: real)



An example instance of the

Students relation



SID Name Login Age GPA

53666 SaNa [email protected] 36 3.7

53668 Kumar [email protected] 34 3.2

53670 Sanath [email protected] 44 3.8


DBMS (cont.….)

• In addition to relational data model…o Hierarchical model

o Network model

o Object oriented model

o Object relational model



Levels of Abstraction in a

DBMS• To illustrate the meaning of data abstraction, consider the example of automotive

design.

• A car designer begins by drawing the concept of the car that is to be produced. Next,

engineers design the details that help transfer the basic concept into a structure that can

be produced. Finally, the engineering drawings are translated into production

specifications to be used on the factory floor.

• As you can see, the process of producing the car begins at a high level of abstraction

and proceeds to an ever-increasing level of detail. The factory floor process cannot

proceed unless the engineering details are properly specified, and the engineering

details cannot exist without the basic conceptual framework created by the designer.




DBMS




DBMS

• DBMS is described at four levels of abstraction:

o External Model

o Conceptual Model

o Internal Model

o Physical Model



Levels of Abstraction in a DBMS:

External Model

• The external model is the end users’ view of the data environment. The term end users refers to people who use the application programs to manipulate the data and generate information. End users usually operate in an environment in which an application has a specific business unit focus.

• Companies are generally divided into several business units, such as sales, finance, and marketing. Each business unit is subject to specific constraints and requirements, and each one uses a data subset of the overall data in the organization.

• Therefore, end users working within those business units view their data subsets as separate from or external to other units within the organization.

• A specific representation of an external view is known as an external schema.

• Because data are being modeled, ER diagrams will be used to represent the external views.




Conceptual Model

• The conceptual model represents a global view of the entire database as

viewed by the entire organization. That is, the conceptual model integrates all

external views (entities, relationships, constraints, and processes) into a single

global view of the data in the enterprise.

• Also known as a conceptual schema, it is the basis for the identification and

high-level description of the main data objects (avoiding any database model–

specific details).

• The most widely used conceptual model is the ER model.

• Generally, the term logical design is used to refer to the task of creating a

conceptual data model that could be implemented in any DBMS.



• Once a specific DBMS has been selected, the internal model maps the conceptual model

to the DBMS.

• The internal model is the representation of the database as “seen” by the DBMS. In

other words, the internal model requires the designer to match the conceptual model’s

characteristics and constraints to those of the selected implementation model.

• An internal schema depicts a specific representation of an internal model, using the

database constructs supported by the chosen database.

• Because the internal model depends on specific database software, it is said to be

software-dependent. Therefore, a change in the DBMS software requires that the

internal model be changed to fit the characteristics and requirements of the

implementation database model.




Internal Model

• The physical model describes the way data are saved on storage media such as disks or tapes. The

physical model requires the definition of both the physical storage devices and the (physical) access

methods required to reach the data within those storage devices, making it both software- and

hardware- dependent.

• The storage structures used are dependent on the software (the DBMS and the operating system) and

on the type of storage devices that the computer can handle.

o Describes storage details

o Summarizes how the relations described in the conceptual schema are actually stored on

secondary storage devices such as disks and tapes

o Decide what file organizations used to store the relations

o Create indexes to speed up data retrieval operations




Physical Model

How does a DBMS do all this?• DBMS is a complex software package and the major components of a

DBMS are shown



Queries In A DBMS

• With reference to a fictitious university database

1. What is the name of the student with student ID

SEU/IS/98/MG/16?

2. What is the average salary of lecturers who teach the

course with course ID MIT22033?

3. How many students are enrolled in course MIT22033?

4. Is there any student with a GPA less than 3.0 enrolled in

course CS564?

• These questions involving the data stored in a DBMS are

called queries



Queries In A DBMS…

• A DBMS provides a specialized language, called the query

language in which queries can be posed

• Relational calculus is a formal query language based on

mathematical logic

• Relational algebra is another formal query language, based

on a collection of operators for manipulating relations, which

is equivalent in power to the calculus



Reference:

Ramakrishnan, R., & Gehrke, J. (2003). Database management

systems. Osborne/McGraw-Hill. (Pp. 03– 23)



Documents

Database Management Systems - sabraz · 11/1/2017 · MIT 22033 Database Management Systems Lesson 01: Introduction By S. Sabraz Nawaz Senior Lecturer in MIT, FMC, SEUSL