DBMS Module 3

7/30/2019 DBMS Module 3

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DBMSData Base Management System



Introduction to DB



What is Database?

It is a collection or single storage of allrelated data files or it is mechanized,centrally-controlled, collection of data



What is the problem of traditional file basesystem? Why DATABASE

Problems of file based systems: Data redundancy and inconsistency

Redundancy - Same data kept in many places Inconsistency – Data in many places but the data do not match

(no updation).

Difficulty in accessing data When the data are kept in many files then this can happen

Data Isolation When attempting to maintain the highest level of isolation , a

DBMS usually acquires locks on data (when accessed more then one

place)

Concurrent access anomalies If same data accessed two places (example bank Rs.1000 balance, Cheaque 2000)

Security problems Any one can take the full database out

Integrity problems Integrity check since the file will accept anything eg:-29/02/1983



Purpose of Database Systems

Database management systems weredeveloped to handle the following difficulties of typical file-processing systems supported byconventional operating systems:

Data redundancy and inconsistency Difficulty in accessing data Data isolation – multiple files and formats Concurrent access by multiple users /Concurrent

access anomalies Security problems Integrity problems



Database Characteristics

Co-ordinated updation To ensure data consistency, each subsystem that participates in

a single transaction must coordinate update operations.

High Quality and Recency of Data belonging to, or occurring at a time immediately before the

present

Data Security means of ensuring that data is kept safe from corruption and that

access to it is suitably controlled.

Data Compatibility data search may reveal multiple sources of similar data

No Data Duplication Data multiply copies

Logical Concept Purposes for creation



DBMS Objectives(5 Objectives)

1. Availability

2. Shareability

3. Evolvability

4. Data Independence

5. Data Integrity



Availability

Data should be available when the user wants to use it for:

Efficient storage, updating and retrieval of

data.

Purposeful information retrevel.



Share ability

Data shared across applications

No data is owned by an application.

Minimization of unplanned redundancy.



Evolvability

Database should evolve with time asapplications and query needs changeswith time.

It is also defined as the capacity of asystem for adaptive evolution



Data Independence

It is the type of data transparency thatmatters for a centralized DBMS. It refersto the immunity of user applications to

make changes in the definition andorganization of data.

Data Independence Types

Physical Independence Logical Independence



Data Independence Types

Physical Independence:

Physical data independence deals with hiding the details of thestorage structure from user applications. The application should notbe involved with these issues, since there is no difference in theoperation carried out against the data.

Logical Independence:

The external scheme may stay unchanged for most changes of the logicalscheme. This is especially desirable as the application software does not

need to be modified or newly translated.



Data Integrity

It refers to the trustworthiness of systemresources over their entire life cycle. In moreanalytic terms, it is "the representationalfaithfulness of information to the true state of theobject that the information represents, whererepresentational faithfulness is composed of four essential qualities or core attributes”: Completeness,

Timeliness,

Accuracy and

Validity



View of Data

An architecture for a database system

View 1

Physical

level

Logical

level

View 2 View n…

View level (DB’s)



Actually, Creating Various DB with DBMS

Personnel Dept.

Emp – Details -1

ECODE (Primary Key)

Name Address

Basic

Grade (confidential info)

Training Needs

Marketing Dept.

Emp – Details -2

ECODE (Primary Key)

Name Job – Assigned

Performance



Full table (information's available to all) no privacy

Full Table

ECODE

Name

Address

Basic

Job-Assigned

Performance

Grade

Training-needs



Creating Various DB using DBMS

LOGICAL (VIEW-1)

Personnel Dept.

Emp – Details -1

ECODE (Primary Key) Name

Address

Basic

Grade (confidentialinfo)

Training Needs

LOGICAL (VIEW-2)

Marketing Dept.

Emp – Details -2

ECODE (Primary Key) Name

Job – Assigned

Performance



Physical View (Stored in DBMS)

ECODE

Name

Address

Basic

Job-Assigned

Performance

Grade

Training-needs



Data Models A collection of tools for describing:

Data Data relationships Data semantics Data constraints

Object-based logical models Entity-relationship model Object-oriented model Semantic model Functional model

Record-based logical models Relational model Network model Hierarchical model



A collection of tools for describing

Data The term data refers to qualitative or quantitative

attributes of a variable or set of variables

Data relationships

A relationship exists between two databasetables when one table has a foreign key thatreferences the primary key of another table.





Data semantics

It is a conceptual data model in which semanticinformation is included. This means that the modeldescribes the meaning of its instances. Such a

semantic data model is an abstraction that defineshow the stored symbols (the instance data) relate tothe real world.

Or

The semantic data model is a software engineeringmodel based on relationships between storedsymbols and the real world.



Data constraints

Database constraints are rules that defineinterrelations between tables and can check andmodify the data in a database.

or Database constraints is the section shows the data

rules that must be followed when entering data in thevarious Domain Name Control Panel fields.



Usernames Allowed characters: A-Z a-z 0-9

Passwords Allowed characters: A-Z a-z 0-9 [ ] ( ) ! @ $ ^ , . ~ | = - + _ ]

Phone Numbersmax 20 characters

Fax Numbersmax 20 characters

Email Addresses

check in Email::Valid

Field Limits*_first_name => 64*_last_name => 64*_org_name => 64*_address1 => 64 (note, conflicts in various areas)

*_address2 => 64 (optional) (note, conflicts in various areas)*_address3 => 64 (optional) (note, conflicts in various areas)*_city => 64*_state => 32*_country => 2*_postal_code => 32 (required) ("na" accepted as a placeholder)*_phone => 20 (note, conflicts in various areas)



Object-based logical models

Entity-relationship model (ER Model)

An entity-relationship model (ERM) is anabstract and conceptual representation of

data. Entity-relationship modeling is adatabase modeling method, used to producea type of conceptual schema or semantic datamodel of a system, often a relationaldatabase, and its requirements in a top-downfashion. Diagrams created by this process arecalled entity-relationship diagrams, ERdiagrams, or ERDs.









Object-Oriented Model

The Object-Oriented Model assists the

programmer to address the complexity of aproblem domain by considering the problemnot as a set of functions that can beperformed but primarily as a set of related,

interacting Objects.



Semantic model

It is a conceptual data model in whichsemantic information is included. This means

that the model describes the meaning of itsinstances(occurrences). Such a semantic datamodel is an abstraction that defines how thestored symbols (the instance data) relate to the real

world

Semantic - meaning that is used to understand human expression through language



Functional model

A function model, also called an activity modelor process model, it is a graphical

representation of an enterprise's functionwithin a defined scope.

The purposes of the function model are todescribe the functions and processes.



Data Definition Language (DDL)

Specification notation for definingthe database schema

DDL compiler generates a set of

tables stored in a data dictionary

Data dictionary contains metadata (data aboutdata)

Data storage and definition language – specialtype of DDL in which the storage structure andaccess methods used by the database systemare specified



Data Manipulation Language (DML)

DML involves both access to andalteration of the contents of database andhence its relations:

Retrieval – via SELECT Statement Insertion – via SELECT Statement

Deletion – via DELETE Statement

Modification – via UPDATE Statement



Language for accessing and manipulatingthe data organized by the appropriate datamodel

Two classes of languages Procedural – user specifies what data is

required and how to get those data

Nonprocedural – user specifies what data isrequired without specifying how to get thosedata



Transaction Management

A transaction is a collection of operations thatperforms a single logical function in a databaseapplication.

Transaction-management component ensuresthat the database remains in a consistent(correct) state despite system failures (e.g.power failures and operating system crashes)and transaction failures.

Concurrency-control manager controls theinteraction among the concurrent transactions,to ensure the consistency of the database.



Storage Management

A storage manager is a program module thatprovides the interface between the low-leveldata stored in the database and the applicationprograms and queries submitted to the system.

The storage manager is responsible for thefollowing tasks:

Interaction with the file manager Efficient storing, retrieving, and updating of data



Database Administrator

Coordinates all the activities of the databasesystem; the database administrator has agood understanding of the enterprise’sinformation resources and needs:

Database administrator’s duties include: Schema definition

Storage structure and access method definition

Schema and physical organization modification

Granting user authority to access the database Specifying integrity constraints

Acting as liaison (communication) with users

Monitoring performance and responding to changes inrequirements



Database Users

Users are differentiated by the way they expectto interact with the system.

Application programmers: interact with system throughDML (Data Manipulation Language).

Specialized users: write specialized databaseapplications that do not fit into the traditional dataprocessing framework

Sophisticated users: form requests in a database querylanguage.

Naive users: invoke one of the permanent applicationprograms that have been written previously



Data Warehouse



What is a Data Warehouse?

A single, complete and consistent store of data obtained from a variety of differentsources made available to end users in a

what they can understand and use in abusiness context.



A process of transformingdata into information andmaking it available tousers in a timely enoughmanner to make adifference

Data

Information

orWhat is Data Warehousing?



Data Warehousing -- It is a process

Technique for assembling and managingdata from various sources for the purposeof answering business questions. Thus

making decisions that were not previouspossible

A decision support database maintained

separately from the organization’soperational database



A data warehouse is a

subject-oriented

integrated time-varying

non-volatile

collection of data that is used primarily in

organizational decision making.



Benefits of a Data Warehouse

A data warehouse maintains a copy of information fromthe source transaction systems.

Maintain data history Integrate data from multiple source systems, enabling a

central view across the enterprise. Improve data, by providing consistent codes and

descriptions. Present the organization's information consistently. Provide a single common data model for all data.

Restructure the data so that it makes sense to thebusiness users. Restructure the data so that it delivers excellent query

performance



Data Mining



Data Mining works with Warehouse Data

Data Warehousing provides the Enterprisewith a memory

Data Mining provides the Enterprise withintelligence



Data Mining

A Process that uses various techniques todiscover “patterns” or knowledge from

data.

Visualization.

Machine Learning algorithms.



Examples

Link Analysis

Frauds detection

New Solutions

Revenue Management

Marketing

Stocks





Thank you…

Documents

DBMS Module 3