01 Intro to Database

Pascasarjana STMIK Nusa Mandiri

PA S C A S A R J A N A S T M I K N U S A M A N D I R I

Introduction to Databases1

Dr. Said Mirza Pahlevi, M.Eng.


I N T R O D U C T I O N T O D ATA B A S E S

Lecture 12



Objectives

Some brief definitions and common uses of database systems.

Characteristics and problems of file-based systems.

Meaning of the term database and Database Management System (DBMS).

Components of DBMS Environment

Roles in the Database Environment

Advantages and disadvantages of DBMSs

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Some Definitions

Database A collection of related data.

Database Management System (DBMS) A software that manages and control accesses to the database.

Database Application A program that interacts with the database at some point in its execution.

Database System A collection of application programs that interact with the database.

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Examples of Database Applications

Purchases from the supermarket Bar code reader app prog DB (update stock number)

Purchases using your credit card Card reader app prog customer DB & stolen DB

Booking a holiday at the travel agents Ensure not to overbook the seat

Using the local library Bar code reader app prog book DB (borrow & return)

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Examples of Database Applications

Taking out insurance

A broker accesses several insurance company databases

Using the Internet

Bookstore to buy books and purchase by using a credit card (both

uses DB)

Studying at university

Student database

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File-Based Systems

Collection of application programs that perform services

for the end users (e.g. reports).

Each program defines and manages its own data.

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File-Based Systems8



Limitations of File-Based Approach

Separation and isolation of data

Each program maintains its own set of data.

Users of one program may be unaware of potentially useful data held

by other programs.

Duplication of data

Same data is held by different programs.

Wasted space and potentially different values and/or different

formats for the same item.

It costs time & money to enter data more than once.

Loss of data integrity.

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Limitations of File-Based Approach

Program – Data dependence File structure is defined in the program code.

It is difficult to change the file structure.

Need to change both the file and accessing programs.

e.g., change PropertyForRent address field from 40 to 41. Creating one-off program & modify all accessing programs

Incompatible file formats Programs are written in different languages (e.g., COBOL & C), and so

cannot easily access each other’s files.

Fixed Queries of application programs Programs are written to satisfy particular functions.

Any new requirement needs a new program.

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Database Approach

The file-based approach limitations arose:

Definition of data was embedded in application programs, rather

than being stored separately and independently.

No control over access and manipulation of data beyond that

imposed by application programs.

Result:

The database and Database Management System (DBMS).

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Database

Definition: shared collection of logically related data and a description of this data, designed to meet the information needs of an organization.

Shared large repository of data with metadata (self-describing).

This enables program–data independence.

Logically related data comprises entities, attributes, and relationships of an organization’s information.

Entities: branch and staff.

Property: branchNo and staffNo.

Relationship: a branch has staff.

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Database Management System (DBMS)

A software system that enables users to define, create,

maintain, and control access to the database.

(Database) application program

A computer program that interacts with database by issuing an

appropriate request (SQL statement) to the DBMS.

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Database Management System (DBMS)

Figure 1.5

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DBMS Functionalities

Data Definition Language (DDL).

Permits specification of data types, structures and any data

constraints.

All specifications are stored in the database.

Data Manipulation Language (DML).

General enquiry facility (query language) of the data.

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DBMS Functionalities

Controlled access to database may include:

A security system

An integrity system

A concurrency control system

A recovery control system

A user-accessible catalog.

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Views

Allows each user to have his or her own view of the

database.

e.g., contract department wants to see for a rental property shown in

Figure 1.5

A view is essentially some subset of the database.

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Views - Benefits

Reduce complexity.

A view based on necessities.

Provide a level of security.

Excluding data that some users should not see.

Provide a mechanism to customize the appearance of the database.

Call field rent as Monthly Rent.

Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed.

Field added or removed, relationships changed, renamed etc.

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Components of DBMS Environment19




Hardware

Can range from a PC to a network of computers.

Client-server architecture (backend & frontend).

Software

DBMS, operating system, network software (if necessary) and also

the application programs (3GL such as Java, VB etc. & 4GL such as

SQL embedded in 3GL).

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Data

Operational data used by the organization and a description of this data called the schema.

Procedures

Instructions and rules that should be applied to the design and use of the database and DBMS.

Log in, start/stop DBMS, backup etc.

People

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Data Administrator (DA)

Manage the data resource (DB planning, conceptual/logical DB

design etc.)

Database Administrator (DBA)

Physical realization of DB (physical DB design & implementation,

security and integrity control etc.)

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Database Designers (Logical and Physical)

Conceptual/logical DB

Identifying the data (entities & attributes), and their relationships &

constraints

Understand the data and business rules (main characteristics of the data

as viewed by the organization)

Physical DB design

Deciding how the logical DB design is to be physically realized

e.g., mapping logical DB design into a set of tables and integrity

constraints

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Application Programmers

Creating program to access the DB (retrieve, insert, update & delete data)

End Users

Naïve: unaware of the DBMS

Sophisticated: familiar with the structure of the database and the provided database facilities

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Advantages of DBMSs

Control of data redundancy Can be duplicated for performance reason

Data consistency Store data in one place

More information from the same amount of data Data integration

Sharing of data The database belongs to the entire organization; not to departments

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Advantages of DBMSs

Improved data integrity (constraints) Validity and consistency of stored data

Improved security Usernames and passwords for authorization

Access by operation types: retrieval, insert, update & delete

Enforcement of standards Data formats, naming conventions, document standards, update procedures and

access rules

Economy of scale Combining operational data into one database and managing them can result in

cost savings

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Advantages of DBMSs

Balance conflicting requirements

The database is under control of a DBA that can make best decisions base on user needs

Improved data accessibility and responsiveness

The integrated data is directly accessible to the end users by using program, query language and report writers

Increased productivity

DBMS provides all the low level file-handling routines (typical in application programs)

Also provides 4th generation environment

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Advantages of DBMSs

Improved maintenance through data independence

DBMS separates data descriptions from the applications

Increased concurrency

DBMS manages concurrent database access

Improved backup and recovery services

Minimize the amount of processing that is lost following a failure

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Disadvantages of DBMSs

Complexity Database design, access policy etc.

Size A large piece of software requiring substantial memory to run

Cost of DBMS Depends on the user number, maintenance cost etc.

Additional hardware costs Disk storage, dedicated machines for DBMS servers etc.

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Disadvantages of DBMSs

Cost of conversion

Converting existing apps to run on new DBMS & hardware

Staff training

Performance

DBMS is developed for general application compared to a file-based system

Higher impact of a failure

Centralization of resource increases the vulnerability of the system.

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01 Intro to Database

Documents

database management

query language

update amp

mirza pahlevi

credit card

application

accessing

end users