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CXB 3104
Advanced Database Systems
Lecture 1
Muthu
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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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