dbms_class _14
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DATABASE MANAGEMENT SYSTEM(DBMS) – CONCEPTS
AND APPLICATIONS
Prof. Ashis Mitra
St. Xavier’s College, Kolkata
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Recruiting Hiring Education & Training
Terminat- ion
Benefit Administration
Potential Employees Employees Retired
Employees
Data Management
The Firm
Primary HR Activities
DATA PROCESSING SYSTEM
A data processing system takes raw data and, through the power of computer automation, produces information that a set of program applications has validated. Information includes text, arithmetic calculations, formulas and various other types of information and data based on the computer system.
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TYPES OF DATA PROCESSING
1. Serial Processing
2. Batch Processing
3. Real time processing
4. Online Processing
5. Centralised Processing
6. Distributed Processing
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• 1. Serial Processing. It is a system in which only one step happens at a time (and so the steps
go in a series).
• 2. Batch Processing. It is used when there is a lot of transactions affecting a high percentage
of master file records and the response needed is not immediate, usually until the end of the
week or month. A good example of this in a large, national business would be payroll
processing, where nearly every master file record will be affected. The data is collected over a
period of time, then input and verified by clerks (verified means input by someone else and
then both inputs are compared by computer) and processed centrally.
• 3. Real-time processing. The waiting time from input to response is minimum. Unreasonable
However such fast systems are used in critical systems that control aircraft or the
manufacture of sensitive or dangerous compounds.
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• 4. Online processing. It means users directly enter information online (usually, online, in this case, means online to a central processor, rather than its modern connotation of the Internet, but it could mean both), it is validated and updated directly onto the master file. No new file is created in this case. Therefore, there is near immediate input process, and output. It is like a booking with travel agents or over the Internet.
• 5. Centralized processing. It is processing performed in one computer or in a cluster of coupled computers in a single location. Access to the computer is via "dumb terminals," which send only input and receive output or "smart terminals," which add screen formatting. All data processing is performed in the central computer.
• 6. Distributed Processing. The distribution of applications and business logic across multiple processing platforms. Distributed processing implies that processing will
• occur on more than one processor in order for a transaction to be completed.
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WHAT IS A DATABASE?
Database is a collection of interrelated data stored in a
database server; these data's will be stored in the form of
tables. The primary aim of database is to provide a way to store
and retrieve database information in fast and efficient manner.
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DATABASE – MAJOR CHARACTERISTICS
• In database approach, a single repository of data is maintained that is defined once and then accessed by many users.
• The database system not only contains data but it contains complete definition or description of the database structure and constraints. These definitions are stored in a system catalog, which contains the information about the structure and definitions of the database.
• The information stored in the catalog is called the metadata, it describes the primary database.
• Database allows multiple users to access the database at the same time and sharing of data is possible.
• Database software allows data to be accessed in a variety of ways and often, by using several programming languages.
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“CRUD”
Refers to the most common Database Operations:
Create
Read
Update
Delete
Operations occur at all levels: Tables, Records, Columns
A DATABASE WITH MULTIPLE TABLES
Training Employee Pay Packet
Placement Perform. Mgt Pay Structure
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DATABASE DESIGN
is a model of structures of reality
supports queries and updates
modeling processes of reality
runs efficiently
The purpose of database design is to create a
database which
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ABSTRACTION
Classification
Aggregation
Generalisation
It is very important that the language used for
data representation supports abstraction.
There are three kinds of abstraction:
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CLASSIFICATION
In a classification we form a concept in a way
which allows us to decide whether or not a
given phenomena is a member of the extension
of the concept.
Employee
Emp 1 Emp 2 Emp 3 Emp 4 Emp 5 Emp 6
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AGGREGATION
In an aggregation we form a concept from existing
concepts. The phenomena that are members of
the new concept’s extension are composed of
phenomena from the extensions of the existing
concepts
Company
Operation
Marketing
Finance
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GENERALIZATION
In a generalization we form a new concept by
emphasizing common aspects of existing concepts,
leaving out special aspects
Employee
Jr. Executive Executive Sr. Executive
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LEVELS OF ABSTRACTION
Physical level describes how a record (e.g., customer) is stored.
Logical level: describes data stored in database, and the relationships among the data.
type Employee = record name : string; Designation : string; EMP Code : integer; end;
View level: application programs hide details of data types. Views can also hide information (e.g., salary) for security purposes.
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DATABASE VIEWS
A View is an individual’s picture of a database. It can be
composed of many tables, unbeknownst to the user.
It’s a simplification of a complex data model
It provides a measure of database security
Views are useful, primarily for READ-only users and are not always safe
for CREATE, UPDATE, and DELETE.
VIEW OF DATA
An architecture for a database system
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USE OF A DATABASE MANAGEMENT SYSTEM
IN DESIGN AND APPLICATION
1-19
Design
Analysis
Design
Verification Evaluation Synthesis Release
HR
Planning HR
Admin
HR
Dev
APPLICATION
DBMS
Database Management
System
Graphic Interface Language Interface INTERFACE
Preliminary-
design
Analysis
Models
Detailed
Design
Design
Release
Control Fabrication
Assembly
Info
Test /
Inspection
Database Manufacturing
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PEOPLE WORKING WITH DATABASES
System Analysts
Database Designers
Application Developers
Database Administrators
End Users
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SYSTEM ANALYSTS
communicate with each prospective database user group in order to understand its
information needs
processing needs
develop a specification of each user group’s information and processing needs
develop a specification integrating the information and processing needs of the user groups
document the specification
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DATABASE DESIGNERS
choose appropriate structures to represent the information specified by the system analysts
choose appropriate structures to store the information in a normalized manner in order to guarantee integrity and consistency of data
choose appropriate structures to guarantee an efficient system
document the database design
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APPLICATION DEVELOPERS
implement the database design
implement the application programs to meet the program
specifications
test and debug the database implementation and the
application programs
document the database implementation and the application
programs
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DATABASE ADMINISTRATORS
Manage the database structure
participate in database and application development
assist in requirement analysis
participate in database design and creation
develop procedures for integrity and quality of data
facilitate changes to database structure
seek communitywide solutions
assess impact on all users
provide configuration control
be prepared for problems after changes are made
maintain documentation
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DATABASE ADMINISTRATORS (CONT.)
Manage data activity
establish database standards consistent with data administration
standards
establish and maintain data dictionary
establish data proponencies
work with data proponents to develop data access and modification
rights
develop, document, and train staff on backup and recovery procedures
publish and maintain data activity standards documentation
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DATABASE ADMINISTRATORS (CONT.)
Manage the database management system generate database application performance reports
investigate user performance complaints
assess need for changes in database structure or application design
modify database structure
evaluate and implement new DBMS features
tune the database
Establish the database data dictionary data names, formats, relationships
cross-references between data and application programs
(see metadata slide)
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END USERS
Parametric end users constantly query and update the database. They use canned transactions to support standard queries and updates.
Casual end users occasional access the database, but may need different information each time. They use sophisticated query languages and browsers.
Sophisticated end users have complex requirement and need different information each time. They are thoroughly familiar with the capabilities of the DBMS.
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