Lec20.pptx introduction to data bases and information systems

Introduction to databases
and Information Systems

Definition
• A database is a logically organized collection of related data
designed and built for a specific purpose.
• A database can be of any size and of any degree of complexity, and it
can be maintained manually or by software on computers.

How Data Is Organized: The Data Storage
Hierarchy
• The data storage hierarchy consists of the levels of data stored in a
computer database: bits, characters (bytes), fields, records, and
files.
• BITS: the bit is the smallest unit of data the computer can store in a
database—represented by 0 for off or 1 for on.
• CHARACTERS: A character (byte) is a letter, number, or special
character. A, B, C, 1, 2, 3, #, $, % are all examples of single characters.
A combination of bits represents a character. Bits and bytes are the
building blocks for representing data.

The Data Storage Hierarchy
• FIELD: A field is a unit of data consisting of one or more characters
(bytes). It is the smallest unit of meaningful information in the
database. Each field has a field name that describes the kind of data
that should be entered into the field. An example of a field is your
first name, or your street address, or your Social Security number.
• RECORD: A record is a collection of related fields. Each record stores
data about only one entity, which can be a person, a place, a thing, an
occurrence or a phenomenon.
• FILE: A file is a collection of related records. An example of a file
would be data collected on everyone employed in the same
department of a company.

Types of Files: Program Files & Data Files
• The file is the collection of data or information that is treated as a unit
by the computer. Files are given names— filenames.
• PROGRAM FILES: FOR SOFTWARE INSTRUCTIONS Program files are
files containing software instructions. Examples are word processing
or spreadsheet programs, which are made up of several different
program files. The two most important are source program files and
executable files.
• DATA FILES: FOR HOLDING DATA Data files are files that contain
data—words, numbers, pictures, sounds, and so on. These are the
files used in databases.

Data Files
• Examples of common extensions in data files are .txt (text) and .xls (Excel
worksheets). Certain proprietary computer programs apply their own
extensions, such as .ppt for PowerPoint and .mdb for Access.
• Three types of files worth particular attention are graphics, audio, and
video files.
• Graphics files: Some important ones are .bmp, .tiff, .gif, .jpeg, and .png.
• Audio files: The ones you’re most apt to encounter are .mp3, .wav, and
.mid.
• Animation/video files: Common files are .qt, .mpg, .wmv, .avi., and .rm.

DATABASE MANAGEMENT SYSTEMS
• A database management system (DBMS), or database manager, is
software written specifically to control the structure of a database
and access to the data. (Strictly speaking, the database is the
collection of the data, and the database management system is the
software—but many professionals use “database” to cover both
meanings.)

The Benefits of Database Management
Systems
• REDUCED DATA REDUNDANCY Data redundancy, or repetition, means that
the same data fields (a person’s address, say) appear over and over again in
different files and often in different formats.
• IMPROVED DATA INTEGRITY Data integrity means that data is accurate,
consistent, and up to date. In the old system, when a change was made in
one file, it might not have been made in other necessary files.
• INCREASED SECURITY Although various departments may share data,
access to specific information can be limited to selected users.
• EASE OF DATA MAINTENANCE Database management systems offer
standard procedures for adding, editing, and deleting records, as well as
validation checks to ensure that the appropriate type of data is being
entered properly and completely into each field type.

The Database Administrator
• Large databases are managed by a specialist called a database
administrator. The database administrator (DBA) coordinates all
related activities and needs for an organization’s database, ensuring
the database’s recoverability, integrity, security, availability, reliability,
and performance.
• Database administrators determine user access privileges; set
standards, guidelines, and control procedures; assist in establishing
priorities for requests; prioritize conflicting user needs; and develop
user documentation and input procedures.

DATABASE MODELS
• Hierarchical Database: In a hierarchical database, fields or records
are arranged in related groups resembling a family tree, with child
(lower-level) records subordinate to parent (higher-level) records.
The parent record at the top of the database is called the root record
or root parent.
• The hierarchical database is the oldest and simplest of the all models.
• It lent itself well to the tape storage systems used by mainframes in
the 1970s. It is still used in some types of passenger reservation
systems.
• In hierarchical databases, accessing or updating data is very fast,
because the relationships have been predefined.

Network Database
• The network database was in part developed to solve some of the
problems of the hierarchical database model. A network database is
similar to a hierarchical database, but each child record can have
more than one parent records.
• Also used principally with mainframes, the network database is more
flexible than the hierarchical arrangement, because different
relationships may be established between different branches of data.
• Although the network database was an improvement over the
hierarchical database, some people in the database community
believed there had to be a better way to manage large amounts of
data.

Relational Database
• More flexible than hierarchical and network database models, the
relational database relates, or connects, data in different files
through the use of a key, or common data element.
• HOW A RELATIONAL DATABASE WORKS In the relational database,
there are no access paths down through a hierarchy. Instead, data
elements are stored in different tables made up of rows and columns.
• In database terminology, the tables are called relations (files), the
rows are called tuples (records), and the columns are called attributes
(fields).

Relational Database
• Whereas in the hierarchical and network database models data is
arranged according to physical address, in the relational model data is
arranged logically, by content.
• Hence, the physical order of the records or fields in a table is
completely immaterial. Each record in the table is identified by a
field—the primary key—that contains a unique value. There are
following two methods through which data can be accessed in
Relational Databases.
• USING STRUCTURED QUERY LANGUAGE
• QUERY BY EXAMPLE

USING STRUCTURED QUERY LANGUAGE
• To retrieve data in a relational database, you specify the appropriate
fields and the tables to which they belong in a query to the database,
using a query language.
• Structured query language ( SQL, pronounced “sequel”) is the
standard query language used to create, modify, maintain, and
query relational databases.
• The three components of a basic SQL query are the SELECT . . . FROM
statement, the WHERE clause, and the ORDER BY clause.
• SELECT PRODUCT-NUMBER, PRODUCT-NAME FROM PRODUCT
WHERE PRICE < 100.00 ORDERBY PRODUCT-NAME;

QUERY BY EXAMPLE
• In query by example (QBE), the user asks for information in a
database by using a sample record form, or table, to define the
qualifications he or she wants for selected records; in other words,
the user fills in a form.
• For example, a university’s database of its student-loan records might
have the column headings (field names) NAME, ADDRESS, CITY, STATE,
ZIP, AMOUNT OWED.
• When you use the QBE method, the database would display an empty
record with these column headings. You would then type in the
search conditions that you want in the appropriate columns

INFORMATION SYSTEMS IN ORGANIZATIONS:
Using Database to Help Make Decisions
• The data in databases is used to build information, and information—
and how it is used—lies at the heart of every organization.
• Of course, how useful information is depends on the quality of it, as
well as the information systems used to distribute it. Let us consider
these subjects.

The Qualities of Good Information
• Correct and verifiable: This means information must be accurate and
checkable.
• Complete yet concise: Complete means information must include all
relevant data. Concise means it includes only relevant data.
• Cost effective: This means the information is efficiently obtained and
understandable.
• Current: Current means timely yet also time sensitive, based on
historical, present, or future information needs.
• Accessible: This means the information is quickly and easily
obtainable

Computer-Based Information Systems
• The purpose of a computer-based information system is to provide managers (and
various categories of employees) with the appropriate kind of information to help them
make decisions.
• It is used to collect and analyze data from all departments and is designed to provide
an organization’s management with up-to-date information at any time.
• There are several types of computer-based information systems, which serve different
levels of management:
• Office information systems
• Transaction processing systems
• Management information systems
• Decision support systems
• Executive support systems
• Expert systems

Information Systems
• Office Information Systems: Office information systems (OISs), also
called office automation systems (OASs), combine various
technologies to reduce the manual labor required in operating an
efficient office environment and to increase productivity.
• Transaction Processing Systems: A transaction processing system
(TPS) is a computer-based information system that keeps track of the
transactions needed to conduct business.
• Management Information Systems: A management information
system (MIS) (pronounced “em-eye-ess”) is a computer-based
information system that uses data recorded by a TPS as input into
programs that produce routine reports as output.

Information Systems
• Decision Support Systems: A decision support system (DSS) is a
computer-based information system that provides a flexible tool for
analysis and helps managers focus on the future.
• Executive Support Systems: executive information system (EIS), an
executive support system (ESS) is an easy-to-use DSS made especially
for strategic managers; it specifically supports strategic decision
making.
• Expert Systems: An expert system, or knowledge-based system, is a
set of interactive computer programs that helps users solve problems
that would otherwise require the assistance of a human expert.

Lec20.pptx introduction to data bases and information systems

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Lec20.pptx introduction to data bases and information systems