Data Base Management System (DBMS) Unit -1 Base Management System (DBMS) Unit -1

MCA 203 , Data Base Management System

© Bharati Vidyapeeth’s Institute of Computer Applications and Management,

New Delhi-63, By Vaibhav Singhal, Asst. ProfessorU1.

© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 1© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 1© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63,By Vaibhav Singhal, Asst. Professor U2.1

Data Base Management System(DBMS)

Unit -1

© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63. 2© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63. 2© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 2© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 2© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63,By Vaibhav Singhal, Asst. Professor U2.2

Data Base Management System

Data: Data is the basic raw,fact and figuresEx: a name, a digit, a picture etc.

Data Base: Collection of related data Ex. the names, telephone numbers and addresses of all

the people you know

Data Base Management System: A DBMS is a set of software

programs that controls the organization, storage, management, and retrieval of data in a database.

Ex: MS-Excel, MS-Access, Oracle, MS SQL, Sybase, IBM DB2


Use of DBMS

Corporate AirlinesHotelsBanksColleges /universityRailway reservationShopping MallsTelecommunication

Industry

Weather forecastingPattern RecognitionData miningSpace ResearchSoftware Industry





Advantages of Using DBMS

Mass Data Storage Centralized Access Automatic Backup Possible Data Recovery Possible Security restrictions can be applied Easily updation & fetching of data Only authorized Access No Data Redundancy Data Consistency etc…….


Flat Files Notepad , WordPad

Light Duty

Medium Duty

Heavy Duty

Database software...


No centralized controlData Redundancy Data Inconsistency Data can not be sharedStandards can not be enforcedSecurity issues Integrity can not be maintainedData Dependence

Disadvantages of Flat File Systems





Controls data redundancy. Enforces user defined rules. Ensures data sharing. It has automatic and intelligent backup and recovery

procedures. It has central dictionary to store information. Pertaining to data and its manipulation. It has different interfaces via which user can

manipulate the data. Enforces data access authorization. Represents complex relationship between data.

Data Base Characteristics


Naive UserA person who does not know what is DBMS.

Like:- A user of ATM. A user of credit card.

Application ProgrammerA programmer who is responsible for developing application programs. This user can make change

in the data base also and can run the queries.

Data Base Users


9

Sophisticated User: sophisticated user interact with the system

without writing programs. Instead, they form their requests in a database query language.

Specialized User:Specialized users are sophisticated users

who write specialized database applications that do not fit into the traditional data- processing framework.

Ex: In expert system, AI, CAD design etc.

Data Base Users contd…..




© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63. 10© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63. 10© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 10© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63 10© Bharati Vidyapeeth’s Institute of Computer Applications and Management, New Delhi-63,By Vaibhav Singhal, Asst. ProfessorU2.10

A database administrator (DBA) is a person responsible for the design, implementation, maintenance and repair of an organization's database.

Data Base Administrator


To Provide space to each user.To create the Physical and logical Schema.To Provide security from unauthorized access.To grant permission to the userInstallation, configuration and upgrading of Oracle

server software and related products.To take Back up and Recovery of data.Performance monitoring of the machine and database.

Roles of Data Base Administrator


Data Base Architecture





Physical Schema

Conceptual Schema

External Schema - 2External Schema - 1 External Schema - 3

Disk

Three-Layer Abstraction


Users Level: At user level different -2 type of users of database are accessing the data by firing their queries.

Conceptual Level:This level is designed by data base administrator. Under this level a schema of data base is created by DBA.This is also known as Logical Level.

Internal Level:It indicates how the data will be stored ad describes the data structures and access methods to be used by data base.

Description of Levels


According to Hoberman (2009),

"A data model is a way finding tool for both business and IT professionals, which uses a set of symbols and text to precisely explain a subset of real information to improve communication within the organization and thereby lead to a more flexible and stable application environment”.

Data Model





Flat file Hierarchical Data Model Network Data model Relational Data model

Different Data Models


This may not strictly qualify as a data model. The flat (or table) model consists of a single, two-dimensional array of data elements, where all members of a given column are assumed to be similar values, and all members of a row are assumed to be related to one another.

Flat Data model


In this model data is organized into a tree-like structure, implying a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list.

Hierarchical Data Model





Example :Hierarchical DBMS

Data is represented by a tree structure

P1 Nut Red 12 London

S2 Jones 10 Paris 300

S1 Smith 20 London 300

P2 Bolt Green 17 Paris

S3 Blake 30 Paris 200

S2 Jones 10 Paris 400


P3 Screw Blue 17 Rome


P4 Screw Red 14 London


Drawbacks: Hierarchical DBMS

Can not handle Many-Many relations

Can not reflect all real life situations

Anomalies in insert, delete and update operations.


Network Data ModelThis model organizes data using two fundamental

constructs, called records and sets. Records contain fields, and sets define one-to-many

relationships between records: one owner, many members.





Relational Data Model

Relational model is based on relations of the tables. It is bounded with 12 codd ’s rules. Every information will be stored in the form of columns

and rows.


Relational Data Model

Example of tabular data in the relational model

customer-name

Customer-idcustomer-street

customer-city

account-number

Johnson

Smith

Johnson

Jones

Smith

192-83-7465

019-28-3746

192-83-7465

321-12-3123

019-28-3746

Alma

North

Alma

Main

North

Palo Alto

Rye

Palo Alto

Harrison

Rye

A-101

A-215

A-201

A-217

A-201

Attributes


Relational Database schema





Poor Table Design


Problems with Design






Name of the Data Models

Relational Model – DB2, Oracle, Informix, Sybase, MS-Access, Foxbase, Paradox, etc.

Hierarchical Model – IMS DBMS

Network Model – IDS & IDMS

Object-Oriented Model – ObjectStore & Versant

Object-Relational Model – Products from IBM, Oracle, ObjectStore, Versant.


• When a schema at a lower level is changed, only the mappings between this schema and higher-lever schemas need to be changed in a DBMS that fully supports data independence. The higher-level schemas themselves are unchanged. Hence, the application programs need not be changed since they refer to the external schemas.

• Disadvantages of two levels of mappings:Overhead during compilation or execution of a query or program

Data IndependenceData Independence


Data IndependenceData Independence

Logical Data Independence: The capacity to change the conceptual schema withouthaving to change the external schemas and their application programs.

Physical Data Independence: The capacity to change the internal schema without having to change the conceptual schema.

Reorganize physical files to improve performancee.g. List all sections offered in Fall 1998





Instance

The collection of information stored in the database at a particular moment is called an instance of the database.

Ex: Amit, 101 etc.


Schema

The overall design of the database is called the database schema.

A schema is the structure of the table which is decided before storing the data.

Example: Create table student( rollno number(5),name char(15),address varchar2(25));


Tuple

A tuple is a related record stored in a row of the table.

Ex: 101,Alok,MCA,85%

Tuple : Record Attributes: columns

Entity : Tables





E-R Diagram

Entity Relationship DiagramSet of some predefined symbols E-R diagram is used to create a relational data base or data model. Before designing the data base we have to first create the E-R Diagram for whole data base than it will convert into the tables and relations.


E-R Diagrams

Rectangles represent entity sets.

Diamonds represent relationship sets.

Lines link attributes to entity sets and entity sets to relationship sets.

Ellipses represent attributes

Double ellipses represent multivalued attributes.

Dashed ellipses denote derived attributes.

Underline indicates primary key attributes (will study later)


Symbols Used in E-R Notation





Summary of Symbols (Cont.)


Cardinality E-R Notations


E-R Diagram With Composite, Multivalued, and Derived Attributes





Types of Keys

Superkey is a set of one or more attributes that allow us to identify uniquely an entity in the entity

set. Like: s.no , name ,age

Candidate Key are minimal superkey in an entity, one of those keys is selected to be the primary key

like: s.no and name both

Primary Key is a candidate key that is chosen to identify entities within an entity set like: rollno

Foreign Key is a primary key of another relation schema like: Any key which is primary key


Weak Entity set

An entity set which is not having any primary key or candidate key is termed a weak entity set.


Strong entity set

An entity set that has a primary key is termed as strong entity set.





Mapping Cardinalities

Express the number of entities to which another entity can be associated via a relationship set.Most useful in describing binary relationship

sets.For a binary relationship set the mapping

cardinality must be one of the following types: One to one One to many Many to one Many to many



One to one One to many

Note: Some elements in A and B may not be mapped to any elements in the other set



Many to one Many to many

Note: Some elements in A and B may not be mapped to any elements in the other set





Overall Database Design


Dr. Edgar F. Codd (1923-2003)

Codd completed his PhD at the University of Michigan in 1963, and presented a thesis on the topic of a self- reproducing computer consisting of a large number of simple identical cells, each of which interacts in a uniform manner with its four immediate neighbors.

Codd reported this work in a book entitled Cellular Automatapublished by Academic Press in 1968.


Relational Terminology





12 Codd's Rules


Rule 1 : The Information Rule

All data should be presented in table form.

Rollno Name Age college

10 Rohit 20 Bv

11 Rahul 21 Abes

12 Amit 22 Jss

13 Simran 23 its


Rule 2 : Guaranteed Access Rule

All data should be accessible without ambiguity.

This can be accomplished through a combination of the table name, primary key and column name.





Rule 3: Systematic treatment of null values

A field should be allowed to remain empty. This involves the support of null value, which is distinct from an empty string or a number with a value of zero.

Most database implementations support the concept of a not –null field constraint that prevent null values in a specific table column.


Rule 4: Dynamic on-line catalog based on the relational model

A relational database must provide access to its structure through the same tools that are used to access the data.

This is usually accomplished by storing the structure definition with in special system table.


Rule 5 : Comprehensive data sub-language Rule

The database must support at least one clearly defined language that include functionality for data definition, data manipulation, data integrity and data transaction control.

All commercial relational databases use forms of standard SQL( structure Query Language) as their supported comprehensive language.





Rule 6 : View updating Rule

Data can be presented into different logical combinations called views.

Each view should support the same full range of data manipulation that has direct access to a table available.

In practical, providing update and delete access to logical views is difficult and is not fully supported by current database.


Rule 7 : High-level Insert, Update and Delete

Data can be retrieved from a relational database in sets constructed of data from multiple rows and multiple tables.

This rule states that insert, update, delete operations should be supported for any retrievable set rather just for a single row in a single table.


Rule 8 : Physical data independence

The user is isolated from the physical method of storing and retrieving information from the database.

Changes can be made to the underlying architecture ( hardware, disk storage methods) without affecting how the user accesses it.





Rule 9 : Logical Data Independence.

How the data is viewed should not be changed when the logical structure (table’s structure) of the database changes.

This rule is difficult to satisfy.

Most databases rely on strong ties between the data viewed and the actual structure of underlying tables.


Rule 10 : Integrity Independence

SQL should support constraints on user input that maintain database integrity.

At a minimum, all databases do preserve two constraints through SQL.

Primary key should be not null and unique.

If a foreign key is defined in one table, any value in it must exist as a primary key in another table.


Rule 11 : Distribution Independence

A user should be totally unaware of whether or not the database is distributed ( whether parts of the database exist in multiple locations).

A variety of reasons make this rule difficult to implement.





Rule 12: The Non subversion rule

There should be no way to modify the database structure other than through the multiple row database language( SQL).

Most databases today support administrative tools that allows some direct manipulation of the data structure.


Specialization

An entity set may include sub grouping of entities that are distinct in some way from other entities in the set.

For Instance, a subset of entities with in an entity set may have attributes that are not shared by all the entities in the entity set.

The process of designating sub grouping with in an entity set is called specialization.


Specialization Example





Generalization

The commonality can be expressed by generalization, which is containment relationship that exists between a higher level entity set and one or more lower level entity sets.

The refinement from an initial entity set into successive level of entity sub grouping represent s a top down design process in which distinctions are made explicit.


Generalization

A bottom-up design process – combine a number of entity sets that share the same features into a higher-level entity set.

Specialization and generalization are simple inversions of each other. They are represented in an E-R diagram in the same way.

The terms specialization and generalization are used interchangeably.


Aggregation

Aggregation is an abstraction through which relationships are treated as higher- level entities.

One limitation of E-R Model is that it can not express relationship among relationship





Aggregation Consider the ternary relationship works-on, which we saw earlier

Suppose we want to record managers for tasks performed by an employee at a branch.


Q1. What is Data Base Management system?A. file B. Tables with recordsC. Software C. none of these

Q2. A data base follows how many rules at max?A. 6 B. 7C. 11 D.11.5

Q3. What is Primary Key?A. NotNull B. UniqueC. Unique +Notnull D. None of these

Objective Questions


Q4. Which is not a DBMS?A. None of the these B. DB2C. Access C. Sybase

Q5. SQL stands for ………………………………Q6. What is candidate Key?

Q7. E- R Diagram is used for what ?

Q8……………….. is specialized user?

Objective Questions





Q9.Logical Data Independency is done at which level?

A. Conceptual Level B. User LevelC. Internal level C. None of the above

Q10. DBA stands for ……………………………

Q11. What is generalization …………………….

Objective Questions


Q.1 What is data independence?Q.2.What do you mean by DBMS?Q.3 A transaction is a set of operations that must be performed completely or not at all.

Explain with suitable example.Q.4What is the difference between Generalization

and Specialization?Q.5 Describe the characteristics of DBMS.Q.6 Explain all components of E-R Diagram.Q.7 What is of keys in DBMS and explain how

many types of keys are there.

Short Questions:


Q.1 Describe 3-level of abstractions of DBMS.Q.2 Differentiate between physical and logical

data independency.Q.3 Discuss all 12 rules of Dr. E.F. Codd’s.Q.4 What is data model? Discuss various data

models available in DBMS.Q.5Differentiate between weak and strong

entity sets with example.Q.6 What is a DBMS? How does it differ from a

conventional file system?

Long Questions:

Documents

Data Base Management System (DBMS) Unit -1 Base Management System (DBMS) Unit -1