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Introduction
to
Database Systems
CS341

C++ and Files
 Why do we need files in programming?
 Files are used to store data
 Data is stored PERMANENTLY
 Files can be used to store Text or binary data
 Data is written or read in the form of input / output operations by
transferring bytes of data
 Steps to use files in your C++ program:
 Determine the type of link required.
 Declare a stream for the desired type of link.
 Attach the desired file to the stream.
 Now process as required
 Close the file-link with stream.
2

What is a Database?
 “A set of information held in a computer”
 Oxford English Dictionary
 “One or more large STRUCTURED sets of
PERSISTANT data, usually associated with software to
update and query the data”
 Free On-Line Dictionary of Computing
 “A collection of data arranged for ease and speed of
search and retrieval”
 Dictionary.com
3

What is a Database (cont.)
 A database is a WELL-ORGANIZED collection of data
that are RELATED in a meaningful way
 A database contains a MODEL of something
 The database contains all the data needed by the
organization
 Several users can access the data in an organization
 Databases are essential to every business
 They are used to
 To maintain internal records
 To present data to customers and clients
 To support commercial processes
4

What is a Database (cont.)
 A database contains a model of something
 How will you model a STUDENT?
 Name ?
 Age ?
 Color of hair ?
 Height ?
 Telephone number ?
 Address ?
 Finger print ?
 Photo ?
5

Examples
 Online Television
 Online streaming service, such as Netflix
 Databases are used to generate a list of TV shows to watch.
 The database tracks an individual’s show preferences, and
provide a list of recommended viewing.
 Social Gaming
 Gaming done across social networks is extremely data intensive.
 Gathering individual player information from around the globe
and serving it to players on demand requires a high availability
database software.
 Personal Cloud Storage
 Sync your devices with data on the cloud requires databases
that are able to call up your data at a moment’s notice
6

Examples (cont.)
 Sports
 Sports fans depend on huge databases full of player statistics.
 This includes game performances, injury reports, and more
 Finances
 Stock market to your local bank use databases
 Tracking the vast amount of information behind the world’s daily
transactions requires extremely powerful databases.
 Organizations
 All organizations need some sort of data in order to do their work
 This data is collected, stored and analyzed using powerful and
far-reaching database services.
7

Examples (cont.)
 Social Media
 Social media platform stores large amount of users’ information
 This data is used to recommend friends, businesses, products,
and topics to the end user.
 eCommerce
 Any online organization that sells its products uses databases.
 This data is stored in highly secure databases
 Healthcare
 Doctor’s offices and healthcare organizations store extensive
amounts of patient data for easy accessibility.
 Weather
 Weather predictions depend on many factors.
 These data are collected, stored and analyzed within databases.
8

Data and Information
 Data are RAW FACTS
 Building block of information.
 Data can be a representation of facts, concepts, or instructions
 INFORMATION is obtained by processing data
 Data has to be interpreted to obtain meaningful information
 “Data” and “Information” are usually used
interchangeably
 Data in database can be broadly classified into two types
 “User Data” collection of information stored and needed by the
organization
 “Metadata” which is the information about the data
9

Data Handling Approaches
 Organizations can use different approaches of Data
Handling
 Common data handling approaches are;
 Manual Approach
 Traditional File Based Approach
 Database Approach
10

Manual Approach
 Manual databases use cards and paper
 Files are used to store information
 Files are labelled and stored in folders and cabinets
 Security is achieved by using Cabinet Lockers
 Insertion and retrieval
 Done by searching for the right cabinet and then for the right file
and information.
 Limitations of the Manual approach
 Error prone
 Difficult to retrieve data and update
 Limited to small size information
 Difficult to related information
 Cross referencing is difficult
11

File-Based Systems
12
File-Based Processing

File-Based Systems (cont.)
 Application programs are responsible for program logic
and data maintenance
 Each program defines and manages its own data
 Data is stored in distinct files provided by OS
 Each file is created and accessed by a separate application
program
 End users can access data via dedicated application
programs only
 Example
 Your C++ program
13

Limitations of File-Based System
The major limitations of a file-based system are:
1. Duplication of Data
2. Data Dependence
3. Incompatible File Formats
4. Separation and Isolation of Data
1. Duplication of Data
 Also termed as Data Redundancy
 The same data being stored more than once by different
programs
 potentially different values and/or different formats for the same item
 Duplication of data leads to loss of data integrity
 Wastage of space
14

Limitations of File-Based System (cont.)
2. Data Dependence
 File structure is defined in the program code
 There is program-data dependence
 Data dependence means the application program depends on a
specific structure of the data
 Data independence is generally preferred as it is more flexible
 Any change in the data structure need to changes the program
as well
 The application program has to be rewritten
15

3. Incompatible File Formats
 The structure of the file depends on the application programming
language.
 Internal Data Structures are different for different Languages
 Example: The Data type INTEGER is not stored in the same manner by
every programming language
 For example, the structure of the file generated by C# program
may be different from the structure of a file generated by “C++”
program
 The incompatibility of such data files makes them difficult to be
accessed by different application programs at the same time
16

4. Separation and Isolation of Data
 Different data is stored in isolated (separate) files.
 It is difficult to manage related data.
 The application programmer must synchronize the processing of
two files to ensure that the correct data are extracted.
 Data distributed in various files may be in different formats hence
it is difficult to share data among different application
17

The Database Approach (cont.)
 Problems of file approach arose because:
 Definition of data was embedded in application programs
 No control over access and manipulation of data beyond that
imposed by application programs
 The DBMS Approach
 A DBMS is a software system that enables users to create,
maintain, and control access to a database
 The same data is shared by different application programs
 Data redundancy is minimized
 Data is stored independent of a specific application programs
 Application can only access the database via the data
management system (DBMS)
19

Database and DBMS
 A Database is a collection of data designed to meet the
information needs of an organization
 Data incudes
 User Data
 A collection of logically related data
 structured data and relationships of an organization’s information.
 Meta Data
 A description of the data itself
 The system catalogue provides description of data to enable program–data
independence.
 Database Management System (DBMS)
 A software system that enables users to define, create, maintain,
and control access to the database.
 Application programs interacts with database by issuing an
appropriate request (SQL statement) to the DBMS
20

The Database System Environment
21

Database System Environment (cont.)
 Hardware
 All the necessary input, output , storage and backup devices
 Can range from a PC to a network of computers.
 Software
 DBMS, operating system, network software (if necessary) and
also the application programs
 Data
 User Data: Data used by the organization and
 Metadata: a description of this data
 People
 Different Roles taken by people while designing and using a
Database systems
22

Database Users
 End users
 Use the database system to achieve some goal
 They are unaware of the DBMS
 Access the database based on their access level and demand
 Access is via application programs or pre-defined queries
 Example: Facebook users
 Application Developers / Programmers
 Write software to allow end users to interface with the database
 They study user requirement to design the data structure
(database) and access methods
 Use SQL to interact with the DBMS
 Example: Developers at Facebook
23

Database Users (cont.)
 Database Administrator (DBA)
 Top-level database expert for an organization
 Designs & manages the database system
 Involved in database planning, development, maintenance of
standards policies and procedures
 Database systems programmer
 Writes the database software (DBMS) itself
 Example: System developers at Oracle, Microsoft, IBM
24

The DBMS
 A DBMS (Database Management System)
 is software that is used to maintain and use a database.
 A DBMS is a software system designed to
 store,
 manage, and
 facilitate access to databases.
 A DBMS is general-purpose software
 Meet the needs of as many applications as possible.
 i.e., not application specific.
 The same DBMS (e.g., Oracle, SQLServer, etc.) can be used in
different systems
 A DBMS takes care of storing and accessing data
 Leaving application specific tasks to application programs
25

The DBMS (cont.)
 Features of the DBMS
 Create the database
 Define security rules
 Server-level
 Database-level
 Share data among several users
 Concurrency control
 Add / Remove data
 Edit the data
 Retrieve the data from the database
 Indexing
 Recovery
 Transaction management, etc.
26

Main Objectives of DBMS
 1 Data Availability
 Data are made available to wide variety of users
 Users should have access to the data in a simple manner
 2 Data Integrity
 refers to the correctness of the data in the database.
 3 Data Security
 Only authorized users should have access to the data
 Different levels of security
 4 Data Independence
 DBMS provides an “abstract view” of how the data is stored in
the database.
 The system hides certain details of how the data are stored and
maintained
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Advantages of DBMSs
 Control of data redundancy
 Data consistency
 Sharing of data
 Improved data integrity
 Improved security
 Enforcement of standards
 Program-data independence
 Increased concurrency
 Improved backup and recovery
 Reduced application development time
 Simple data administration
28

Disadvantages of DBMSs
 Complexity
 Size
 Cost of DBMS
 Additional hardware costs
 Cost of conversion
 Performance
 Higher impact of a failure
29

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Comprehensive Guide to Effective Introduction to Database Systems Principles

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