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CXB 3104

Advanced Database Systems

Lecture 1

Muthu

muthma@sunway.edu.my

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Outline

Data & Information

Database

Types of database

Database Schema

Database models

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Data

Data can be classified as raw facts or the

building block of information.

These are usually unprocessed information.

Data can exists in a variety of forms such as

numbers or text on pieces of paper and

bytes stored in electronic memory, or as

facts stored in a persons mind.

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Metadata describes how and when and by

whom a particular set of data was collected,and how the data is formatted.

Meta data

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Information can be classified as processed

data.

Information should be meaningful, relevant,

accurate and timely.

These are essential ingredients to good

decision-making, which is the key to

organizational success.

Information

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Data Management is a discipline that

focuses on the proper generation, storage

and retrieval of data

Data management

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What is a database?

A collection of information organized in

such a way that a computer program can

quickly select desired pieces of data.

Databases are organized as fields, records,

and files.

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Database organization

A field is a single piece of information that

has a specific meaning and is used to

define and store data.

A record is one complete set of fields

describing a person, place or thing.

A file is a collection of related records.

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Database management system

To access information from a database, you

need a database management system

A DBMS is a collection of programs that

enables you to store, modify, and extract

information from a database.

DBMSs makes data management moreeffective

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Advantages of DBMS

The end-users has better access to more

and better-managed data.

Allows integrated view of organizations

data leading.

The ability to produce quick responses to

ad hoc queries.

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DBMS Facilities

Data Manipulation Language

has a central repository for all data and data

descriptions

provides inquiry facilities to this data called a

query language.

Data Definition Language

allows users to specify the data-type and

structures, and the constraints on that data to

be stored in the database

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Types of Databases

Single-userdatabase

Desktop database

Multi-userdatabase

Workgroup database

Enterprise database

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A centralized database is one that supports datalocated at a single site.

A distributed database is a single logical database thatis spread physically across computers in multiplelocations

The transactional database is used to processtransactions

A data-warehouse database focuses on storage ofdata that will be used for information generation for the

purpose of decision-making.

Other classifications of Databases

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Database Design

Database design refers to the design of the database

structure that will be used to store and manage data.

It does NOT refer to the designing the DBMS software.

A well- designed database will minimize the problem of

data-redundancy.

A poorly designed database tends to generate errors

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Schema

Database Schema:

The description of a database.

Includes descriptions of the database

structure, data types, and the constraints on

the database.

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Database Schema vs. Database State

Distinction

The database schema changes very

infrequently.

The database state changes every time the

database is updated.

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Example of a Database Schema

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Example of a database state

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Three-Schema Architecture

Proposed to support DBMS

characteristics of:

Program-data independence.

Support ofmultiple views of the data.

Not explicitly used in commercial DBMS

products, but has been useful in explaining

database system organization

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Three-Schema Architecture

Defines DBMS schemas at three levels:

Internal schema at the internal level to describe physical

storage structures and access paths (e.g. indexes).

Typically uses a physical data model.

Conceptual schema at the conceptual level to describe

the structure and constraints for the whole database for a

community of users.

Uses a conceptual or an implementation data model.

External schemas at the external level to describe the

various user views.

Usually uses the same data model as the conceptual schema.

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The three-schema architecture

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Data Independence

Logical Data Independence:

The capacity to change the conceptualschema without having to change the externalschemas and their associated applicationprograms.

Physical Data Independence:

The capacity to change the internal schemawithout having to change the conceptualschema.

For example, the internal schema may bechanged when certain file structures arereorganized or new indexes are created toimprove database performance

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A clear description of a policy, procedure, or principlewithin an organizations environment.

Properly written business rules are used to define entities,attributes relationships and constraints.

To be effective, a business rule must be easy to understandand widely disseminated to ensure that every person in theorganization shares a common interpretation.

Business rules

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Examples

A customer may generate many invoices.

Only one customer generates each invoice.

A minimum of 15 participants is needed for the

training to be scheduled

Business rules

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They help standardize the companys view of data.

They constitute a communications tool between users

and designers.

They allow the designer to understand the nature, role

and scope of all data.

They allow the designer to understand business

processes.

They allow the designer to develop appropriate

relationship participation rules and constraints. .

Business rules Why?

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Records are arranged in a top-down

structure

The parent and child are often used in

describing hierarchical model

a child is related to only one parent

Hierarchical Model

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Hierarchical Model

DEPARTMENT

DEPTNO DNAME LOCATION

D NA ME A GE C OD E S NA ME N OY EA RS

IDENT COST NUMBER

EQUIPMENT EMPLOYEE

SKILLDEPENDENT

EMPNO ENAME YEARS

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Network Data Model

no distinction between parent and child recordtypes

Any record type may be associated with any number ofdifferent record types

network schema - the conceptual organization of theentire database as viewed by the database administrator.

The subschema, which defines the portion of thedatabase seen by the application programs thatactually produce the desired information from the datacontained in the database.

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DEPARTMENT

EMPNO ENAME YEARS

DEPTNO DNAME LOCATION

EMPLOYEE PROJECT

PROJNO DESCRIPTION

DEPT-EMP DEPT-PROJ

PROJ-EMP

Network Data Model

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Relational Model

Based on the mathematical concept of a relation, represented as atable.

A table stores a collection of related entities.

The database resembles a file but a unlike a file a table yields completedata and structural independence because it is purely logical.

How the data is stored in the database is of no consequence to the useror designer.

A table is a matrix made up a series of row and columns.

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Relational Model

Bno. Street location PostCode TelNo.

B1 22, Oxley Rd Central 589652 67894561

B2 44, Shenton Way South 548796 67896325

B3 11, Chai Chee Rd East 585698 67665892

B4 4, Jurong West Drive West 526478 68875425

Sno.

F name L na me P os it io n Sal ar

y

Sex Bno

S11 John Doe Manager 5000 M B1

S12 Stella Chan Clerk 1800 F B3

S14 Muthu Ramasam

y

Senior Exec 3200 M B3

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Structural Independence

Improved conceptual simplicity

Easier design, implementation and

management

Ad hoc query capability

Powerful DBMS

Advantages of the Relational model

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Substantial overhead

Can facilitate poor design and implementation

Promote islands of information problem

Disadvantages of the Relational

model

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Object-oriented Model

Objects are abstraction of the real world

entities that exhibit states and behaviors

state of objects is expressed as values of the

attributes of the object

behavior of an object is expressed by a set of

methods that operate on its attributes.

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Features of OO data model

An object is an abstraction of real-world entity. It represents a singleoccurrence of an entity.

Attributes describe the properties of an object. Objects that sharesimilar characteristics are grouped in classes.

A class is a collection of similar objects with shared structure.

A methodrepresents a real-world action such as display; to print out thedetails of the Student. Methods define the behavior of an object.

Classes are organized in a class hierarchy.

Inheritance is the ability of an object within the class hierarchy to inheritthe attributes and methods of classes above it(parent).

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Advantages of the OO model

Add semantic content

Visual presentation includes semantic content.

Database integrity

Both structural and data independence

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Slow pace of OODM standards and development

Complex navigational data access

Steep learning curve

High systems overhead slows transactions .

Disadvantages of the OO model

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Relational Database Model

Relational Database Model

View of data is logical rather than physical.

DBMS in between the application and

database allows the designer to focus on the

logical representation of the data and their

relationships.

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Logical view of the relational database is

facilitated by the creation of relationships

based on a logical construct known as atable or a relation.

Tables

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A table is composed of rows and columns.

Each row (tuple) represents a single occurrence.

Each column represents an attribute and is uniquelynamed.

Each row/column intersection represents a single piece ofdata.

All values in a single column must be of the same dataformat.

The range of possible values of a column is known as theattribute domain.

Each table must have an attribute or combination of

attributes that uniquely identifies each row.

Table characteristics

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Table - example

Bno. Street location PostCode Tel No.

B1 22, Oxley Rd Central 589652 67894561

B2 44, Shenton Way South 548796 67896325

B3 11, Chai Chee Rd East 585698 67665892

B4 4, Jurong West Drive West 526478 68875425

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Candidate KeyIt is an attribute or combination of attributes thatenables each row to be uniquely identified.

Primary keyIt is an attribute or a set of attributes that uniquelyidentify a specific instance of an entity.

Composite KeyIt is a primary key that made up of more than oneattribute.

Secondary keyAn attribute or combination of attributes usedstrictly for data retrieval purposes.

Foreign Key- An attribute whose values match primary key values inthe related table

Relational Keys

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Relational Keys

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Integrity rules

Entity integrity

primary key can never be a null value

used to identify a unique row in a relational table

its value must always be specified.

insert, update, and delete operations maintain the

uniqueness and existence of all primary keys.

Referential integrity

A foreign key, must either be null or match the values in

the relational table in which that foreign key is a primary

key.

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Relational tables are sets.

Rows of the tables can be considered as

elements of the set

Operations that can be performed on sets

can be done on relational tables.

Relational Data Manipulation

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