Introduction Database Concepts - swatitechsol.com · Introduction Database Concepts CO attained :...

Introduction Database Concepts

CO attained : CO1

Hours Required: 05

Self Study: 08

Prepared and presented by :

Ms. Swati Abhang

Contents

Introduction

Characteristics of databases,

File system V/s Database system,

Users of a Database system

Data Models, Schemas, and Instances,

Three-Schema Architecture and Data Independence,

Database Administrator (DBA), Role of a DBA

What is a Database System?

1-3

Application

program

End-user

DBMS

What is a DATABASE?

Definition

A database is a well organized collection of data that

are related in meaningful way which can be accessed in a

different logical orders but are stored only once. The data in

the database is therefor integrated, structured and shared.

What is a Database System? (cont.)

1-5

Major components of a database system: Data: integrated and shared.

Hardware: disk, CPU, Main Memory, ...

Software: DBMS

Users:

1. Application programmers

2. End users

3. Database administrator (DBA)

Defining external schema

Defining conceptual schema

Defining internal schema

Liaison with users

Defining security and integrity checks

Defining backup and recovery procedures

Monitoring performance and changing requirements

Why Database ?

1-6

Redundancy can be reduced

Inconsistency can be avoided

The data can be shared

Standards can be enforced

Security restrictions can be applied

Integrity can be maintained

Provision of data independence

objective !

Characteristics of databases

Persistent Data

Metadata and self-describing Nature

Data Independence

Access flexibility and Security

Characteristics of dbms

To incorporate the requirements of the organization,

system should be designed for easy maintenance.

Information systems should allow interactive access to

data to obtain new information without writing fresh

programs.

System should be designed to co-relate different data to

meet new requirements.

An independent central repository, which gives

information and meaning of available data is required.

1-8

Characteristics of dbms

Integrated database will help in understanding the inter-

relationships between data stored in different applications.

The stored data should be made available for access by

different users simultaneously.

Automatic recovery feature has to be provided to

overcome the problems with processing system failure.

1-9

1-10

Functions of the DBMS

Data Definition Language (DDL)

Data Manipulation Language (DML)

Data Security and Integrity

Data Recovery and Concurrency

Data Dictionary

Performance

History of Database Systems

1950s and early 1960s:

Data processing using magnetic tapes for storage

Tapes provided only sequential access

Punched cards for input

Late 1960s and 1970s:

Hard disks allowed direct access to data

Network and hierarchical data models in widespread use

Ted Codd defines the relational data model

Would win the ACM Turing Award for this work

IBM Research begins System R prototype

UC Berkeley begins Ingres prototype

High-performance (for the era) transaction processing

History (cont.)

1980s: Research relational prototypes evolve into commercial systems

SQL becomes industrial standard

Parallel and distributed database systems

Object-oriented database systems

1990s: Large decision support and data-mining applications

Large multi-terabyte data warehouses

Emergence of Web commerce

Early 2000s: XML and XQuery standards

Automated database administration

Later 2000s: Giant data storage systems

Google BigTable, Yahoo PNuts, Amazon, ..

Database: Historical Roots

Manual File System

to keep track of data

used tagged file folders in a filing cabinet

organized according to expected use

e.g. file per customer

easy to create, but hard to

locate data

aggregate/summarize data

Computerized File System

to accommodate the data growth and information need

manual file system structures were duplicated in the computer

Data Processing (DP) specialists wrote customized programs to

write, delete, update data (i.e. management)

extract and present data in various formats (i.e. report)

S511 Session 2, IU-SLIS 13

File System: Example


Database Systems: Design, Implementation, & Management: Rob & Coronel

File System: Weakness Weakness

“Islands of data” in scattered file systems.

Problems Duplication

same data may be stored in multiple files

Inconsistency

same data may be stored by different names in different format

Rigidity

requires customized programming to implement any changes

cannot do ad-hoc queries

Implications Waste of space

Data inaccuracies

High overhead of data manipulation and maintenance


File System: Problem Case


CUSTOMER file AGENT file SALES file

A_Name (15 char)

Carol Johnson

A_Name (20 char)

Carol T. Johnson

AGENT (20 char)

Carol J. Smith

- inconsistent field name, field size - inconsistent data values - data duplication

Database System vs. File System



Hierarchical Database

Background

Developed to manage large amount of data for complex manufacturing projects

e.g., Information Management System (IMS)

IBM-Rockwell joint venture

clustered related data together

hierarchically associated data clusters using pointers

Hierarchical Database Model

Assumes data relationships are hierarchical

One-to-Many (1:M) relationships

Each parent can have many children

Each child has only one parent

Logically represented by an upside down tree


Hierarchical Database: Example



Hierarchical Database: Pros & Cons

Advantages Conceptual simplicity

groups of data could be related to each other

related data could be viewed together

Centralization of data

reduced redundancy and promoted consistency

Disadvantages Limited representation of data relationships

did not allow Many-to-Many (M:N) relations

Complex implementation

required in-depth knowledge of physical data storage

Structural Dependence

data access requires physical storage path

Lack of Standards

limited portability


Data Manipulation Language (DML)

Language for accessing and manipulating the data

organized by the appropriate data model

DML also known as query language

Two classes of languages

Procedural – user specifies what data is required and how to

get those data

Declarative (nonprocedural) – user specifies what data is

required without specifying how to get those data

SQL is the most widely used query language

Data Definition Language (DDL)

Specification notation for defining the database schema Example: create table account (

account_number char(10),

branch_name char(10),

balance integer)

DDL compiler generates a set of tables stored in a data dictionary

Data dictionary contains metadata (i.e., data about data) Database schema

Data storage and definition language Specifies the storage structure and access methods used

Integrity constraints Domain constraints

Referential integrity (e.g. branch_name must correspond to a valid branch in the branch table)

Authorization

Users of Database system

Database Users

Database Administrators

In a database environment, the primary resource is the

database itself and the secondary resource is the DBMS and

related software

authorizing access to the database

coordinating and monitoring its use

acquiring software and hardware resources as needed

Database Designers

identifying the data to be stored in the database

choosing appropriate structures to represent and store this

data undertaken before the database is actually implemented

and populated with data

Database Users …..

communicate with all prospective database users, in order to understand their requirements

develop a view of the database that meets the data and processing requirements for each group of users

These views are then analyzed and integrated with the views of other user groups. The final database design must be capable of supporting the requirements of all user groups

End Users

access to the database for querying, updating, and generating reports

Casual end users: occasionally access the database

need different information each time

learn only a few facilities that they may use repeatedly.


use a sophisticated database query language to specify their requests

typically middle- or high-level managers or other occasional browsers

Naive or parametric end users constantly querying and updating the database, using standard types of queries and

updates called canned transactions that have been carefully programmed and

tested

need to learn very little about the facilities provided by the DBMS

Bank tellers check account balances and post withdrawals and deposits

Reservation clerks for airlines, hotels, and car rental companies check availability

for a given request and make reservations

Clerks at receiving stations for courier mail enter package identifications via bar

codes and descriptive information through buttons to update a central database of

received and in-transit packages


Sophisticated end users Engineers, scientists, business analysts, and others who

thoroughly familiarize themselves with the facilities of the DBMS so as to implement their applications to meet their complex requirements

Try to learn most of the DBMS facilities in order to achieve their complex requirements

Stand-alone users Maintain personal databases by using ready-made program

packages that provide easy-to-use menu- or graphics-based interfaces. An example is the user of a tax package that stores a variety of personal financial data for tax purposes

Typically become very proficient in using a specific software package


System Analysts and Application Programmers

Determine the requirements of end users, especially naive and

parametric end users, and develop specifications for canned transactions

that meet these requirements

Application programmers implement these specifications as programs;

then they test, debug, document, and maintain these canned transactions

Workers behind the Scene

Typically do not use the database for their own purposes

DBMS system designers and implementers

design and implement the DBMS modules (for implementing the catalog,

query language, interface processors, data access, concurrency control,

recovery, and security. ) and interfaces as a software package


Tool developers

Tools are optional packages that are often purchased

separately

include packages for database design, performance monitoring,

natural language or graphical interfaces, prototyping, simulation,

and test data generation.

Operators and maintenance personnel

system administration personnel who are responsible for the

actual running and maintenance of the hardware and software

environment for the database system

Data Models

A collection of tools for describing Data Data relationships Data semantics Data constraints

Relational model

Entity-Relationship data model (mainly for database design)

Object-based data models (Object-oriented and Object-relational)

Semistructured data model (XML)

Other older models: Network model Hierarchical model

Relational Model

All the data is stored in various tables.

Example of tabular data in the relational model Columns

Rows

A Sample Relational Database

Instances and Schemas

Similar to types and variables in programming languages

Logical Schema – the overall logical structure of the database Example: The database consists of information about a set of customers

and accounts in a bank and the relationship between them Analogous to type information of a variable in a program

Physical schema– the overall physical structure of the database

Instance – the actual content of the database at a particular point in time Analogous to the value of a variable

Physical Data Independence – the ability to modify the physical schema without changing the logical schema Applications depend on the logical schema

In general, the interfaces between the various levels and components should be well defined so that changes in some parts do not seriously influence others.

Architecture of DBMS

Following are the three levels of database

architecture,

1. Physical Level

2. Conceptual Level

3. External Level

Three Levels

Architecture

of DBMS

Mapping is the process of transforming request response

between various database levels of architecture.

Mapping is not good for small database, because it takes

more time.

In External / Conceptual mapping, DBMS transforms a

request on an external schema against the conceptual

schema.

In Conceptual / Internal mapping, it is necessary to

transform the request from the conceptual to internal

levels.

1. Physical Level

Physical level describes the physical storage structure of data in database.

It is also known as Internal Level.

This level is very close to physical storage of data.

At lowest level, it is stored in the form of bits with the physical addresses on the secondary storage device.

At highest level, it can be viewed in the form of files.

The internal schema defines the various stored data types.

It uses a physical data model.

2. Conceptual Level

Conceptual level describes the structure of the whole

database for a group of users.

It is also called as the data model.

Conceptual schema is a representation of the entire

content of the database.

These schema contains all the information to build

relevant external records.

It hides the internal details of physical storage.

3. External Level

External level is related to the data which is viewed by

individual end users.

This level includes a no. of user views or external

schemas.

This level is closest to the user.

External view describes the segment of the database that

is required for a particular user group and hides the rest

of the database from that user group.

Architec

ture of

DBMS

/Databa

se

System

Internal

s

Responsibilities of DBA

Installation, configuration and upgradation of databases like Microsoft SQL/ MySQL/ Oracle Server Software.

Evaluating the features of various databases.

Establishing and maintaining sound backup and recovery policies and procedures.

Taking care of database design and implementation.

Implementing and maintaining the database security.

Database tuning, application tunning and performance monitoring.

Maintaining documentation and standards.

DBA does some technical trouble shooting and consultation to development teams.

Skill set is required to be a successful

Database Administrator

Problem Management

Incident Management

Chain Management

Capacity Planning

Types of DBA

1. Administrative DBA

2. Development DBA

3. Architect

4. Data Warehouse DBA

5. OLAP DBA

Types of DBA

1. Administrative DBA

Administrative DBA maintains the work on the server and

keeps it running.

Administrative DBA is mostly concerned with backups,

security, replication etc.

2. Development DBA

Development DBA builds queries, stored procedures etc.

which mostly meet business needs.

Development DBA is equivalent to a programmer.

Types of DBA

3. Architect

Architect builds table, design schema, foreign keys, primary keys

etc. which meets the business needs.

4. Data Warehouse DBA

Data Warehouse DBA is responsible for merging the data from

multiple sources into a data warehouse.

5. OLAP DBA

OLAP DBA builds multi-dimensional cubes for decision

support or OLAP systems.

The primary language in SQL Server is MDX.

Important Questions

1. What is a database ? Discuss its main features and explain the importance of each feature .

2. List the characteristics of databases.

3. Describe the disadvantages of using a file processing system compared to a database system ?

4. What is DBMS ? What task does a DBMS carry out ?

5. What are classes of users use database systems?

6. List three views for database system in three level architecture. Describe role of these views.

7. List the major components of DBMS architecture and describe their functions.

8. Describe role of DBA

What is meant by logical and physical structure of data ?

Explain difference between logical and physical

independence ?

Explain difference between external, internal and

conceptual view in three-tier database architecture. How

are these different schema layers related to the concept

of logical and physical data independence.

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