1

DATABASE

By

Mr. Abdalla A. Shaame

What is a database?

The main characters of a database system

The basic database design method

The entity-relationship data model for application modeling

2

3

Types of databases

• traditional

• multimedia - pictures, video, sound

• Scientific database

- GIS: maps, weather, satellite images

- biological database: DNA sequence analysis

• warehouse, OLAP - analysis, decision making

• real-time, active databases - industrial processes

• deductive databases - combination of inference and databases

4

Database

• collection of related data

• represents some aspect of the real world

• built with a specific purpose in mind

• could be anywhere - notebook, spreadsheet, Access, Oracle, … could be manual / could be computerized

Data

• known and recordable facts• name, phone number, address, grade, ...

A database system is composed of four components;

DataHardwareSoftwareUsers

5

6

7

Database Management System (DBMS)

• collection of software facilitating the definition,

construction and manipulation of databases

Definition•record structure•data elements

•names•data types•constraints

etc

Construction•create database

files•populate the

database with records

Manipulation•querying•updating

8

Database Management System (DBMS)

• collection of software facilitating the definition, construction and manipulation of databases

Users/actors

Requestmanager

Storagemanager

Meta data

Storeddatabase

DBMS

9

Sample database

Student Name StNo Class Major

Smith 17 1 CS

Brown 8 2 CS

Course CName CNo CrHrs Dept

Database 8803 3 CS

C 2606 3 CS

Section SId CNo Semester Yr Instructor

32 8803 Spring 2000 Smith

25 8803 Winter 2000 Smith

43 2606 Spring 2000 Jones

Grades StNo Sid Grade

17 25 A

17 43 B

file1file2

file3

file4

10

Characteristics of the Database approach

• single repository of data• sharable by multiple users

•concurrency control•transaction control

• self-describing - system catalogue contains meta data

• program-data independence• some changes to the database are transparent to

programs/users

• multiple views of data - to support individual needs of programs/users

11

Database Actors

• Database Administrator (DBA)- authorizing access to the database

- coordinating and monitoring its use- aquiring software and hardware as

needed - solving problems such as breach of security or poor system performance

• Database Designers/Modelers- identifying the data to be stored

- choosing appropriate data structure

• End-users- access to the database: querying, updating,

generating reports

• Software Engineers- developing application programs

12

Advantages of the Database approach(capabilities we would look for in a DBMS)

• controlled redundancy• database design integrates different user data needs• performance tuning may lead to replicated data

• Sharing of the data

• controlled/authorized access to data

• Ensure integrity of the data

• backup and recovery

13

Implications of the Database approach

• standards enforcement• DBA can enforce standard naming conventions, etc

• reduced application development time• adding new functionality to an existing database is

“easy”

• flexibility• adding new data and making some types of changes is

“easy”

• up-to-date information - due to sharable characteristic

• economies of scale - due to sharable resources the wholeorganization can make one investment

14

When not to use a DBMS

• overhead costs are too great

• high initial investment

• data and applications are simple, well-defined, not expected to change

• stringent real-time constraints

• multi-user environment not needed

15

Database design

• let’s jump ahead to see this

Grades

Student

Delivery

1

N

Course

SectionN

M

16

Database design

• let’s jump ahead to see this

Grades

Name

Major

Student

StNo

Class

Delivery

Course

Section

1

N

N

M

17

Database design

• let’s jump ahead to see this

Grades

Name

Major

CName

CNo

Student

StNo

Class

Delivery

Course

Section

CrHrs

Dept

1

N

N

M

18

Database design

• let’s jump ahead to see this

Grades

Name

Major

CName

CNo

Instructor

Semester

Year

SId

Student

StNo

Class

Delivery

Course

Section

CrHrs

Dept

N

1

NM

19

Database design

• let’s jump ahead to see this

grade

Grades

Name

Major

CName

CNo

Instructor

Semester

Year

SId

Student

StNo

Class

Delivery

Course

Section

CrHrs

Dept

1

N

N

M

20

employee

department

project

dependent

With attributes, etc:

works for

manages

works on

dependents of

controls

supervision

bdate

ssn

name

lnameminitfname

sex address salary

birthdatename sex relationship

name number location

name number location

number ofemployeesstartdate

hours

1

1

1

N

supervisor

supervisee M

N

11

NNdegree

1 N

21

ER-to-Relational mapping

1. Create a relation for each strong entity type

2. Create a relation for each weak entity type• include primary key of owner (an FK - foreign key)• owner’s PK + partial key becomes PK

3. For each binary 1:1 relationship choose an entity and include the other’s PK in it as an FK. Include any attributes of the relationship

4. For each binary 1:n relationship, choose the n-side entity and include an FK of the other entity. Include any attributes of the relationship

22

5. For each binary M:N relationship, create a relation for the relationship• include PKs of both participating entities and any

attributes of the relationship• PK is the concatenation of the participating entity PKs

6. For each multivalued attribute create a new relation• include the PK attributes of the entity type• PK is the PK of the entity type and the multivalued

attribute

7. For each n-ary relationship, create a relation for the relationship• include PKs of all participating entities and any attributes

of the relationship• PK may be the concatenation of the participating entity

PKs