4190.301; Spring 2009
Prof. Sang-goo Lee
((13:00pm:
p Mon & Wed: Room 302-208))
INTRODUCTION TO
DATABASE SYSTEMS
Syllabus
ƒ
Text Book
ƒ
Exams (tentative dates)
‚ Midterm Exam: 4/22 (Wed)
‚ Final Exam: 6/10 (Wed)
Database System Concepts, 5th Edition, A.
Silberschatz, H. F. Korth, and S. Sudarshan,
McGraw Hill, 2006.
ƒ
à
ƒ
ƒ
Rf
Reference
à
à
‚ 2~3 programming assignments
‚ To be announced later
Database Systems, Atzeni, et al, McGraw
Hill, 2000.
Lecture Notes
à
T
Term
Project
P j
ƒ
Grades
will be posted before class at
http://europa.snu.ac.kr
username & password required
Please use only for personal use
‚ Exams: 30% each
‚ Term Projects: 30% total
‚ Quizzes, Assignments, etc: 10%
A score of 0 in
• any one of the exams, or
• more than 50% of your reports, projects, or
assignments/quizzes
will result in F.
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 2
CHAPTER 1.
INTRODUCTION
Contents
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ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Data & Database
Database Management Systems
View of Data
Data Models
Data Languages
Database Users
Transaction Management
S
Storage
M
Management
Data Mining & Analysis
Overall System Structure
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 4
Data & Database
ƒ Data
à
A fformall description
d
i ti off
‚ an entity, event, phenomena, or idea
‚ that is worth recording
ƒ Database
An integrated collection of
persistent
i
d
data
representing the information of interest
for various programs that compose the computerized information system of an
organization.
organization
à Data are separated from the programs that use them
à
à
à
à
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 5
What is a Database? Examples!
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 6
What do we do with it?
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 7
What do we do with it? (cont.)
ƒ Most (all?) computing applications use some type of a database
CRM
ERP
MIS
Data Mining
E-Commerce
ERP
Database
Database
b
Original Slides:
© Silberschatz, Korth and Sudarshan
Database
Database
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 8
Database Management System (DBMS)
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Warehouse
Chap 1 - 9
Database Management System (DBMS)
WH
manager
WH
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 10
Database Management System (DBMS)
Database
Order processing
Employee
Products
Customer
Users
DBMS
Payroll
Analytic Reports
Inventory
Sales
Applications
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 11
Database Management System (DBMS)
ƒ Set of programs to access the data
ƒ DBMS provides
id an environment
i
t that
th t is
i both
b th convenient
i t andd efficient
ffi i t
to use.
ƒ Database Applications (Information Systems):
à
à
à
à
à
à
Banking: all transactions
Airlines: reservations, schedules
U i
Universities:
iti
registration,
i t ti grades
d
Sales: customers, products, purchases
Manufacturing: production, inventory, orders, supply chain
Human resources: employee
l
records,
d salaries,
l i tax deductions
d d i
ƒ Databases touch all aspects of our lives
ƒ Commercial Systems
à
à
DB2, Oracle, Informix, BADA, MS SQL Server, Sybase,
dBase, FoxPro, Access
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 12
File Systems
ƒ File System
à
à
à
Part of OS
Stores programs, data, documents, or anything
(in disk)
ƒ In the early days,
days database applications were built on top of file systems
ƒ Drawbacks of using file systems to store data:
Data redundancy and inconsistency
‚ Multiple file formats, duplication of information in different files
à Difficulty in accessing data
‚ Need to write a new p
program
g
to carryy out each new task
à Data isolation — multiple files and formats
à Integrity problems
‚ Integrity constraints (e.g. account balance > 0) become part of program code
‚ Hard to add new constraints or change existing ones
à
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 13
File Systems (cont.)
ƒ Drawbacks of using file systems (cont.)
Atomicity
At
i it off updates
d t
‚ Failures may leave database in an inconsistent state with partial updates carried
out
‚ E.g. transfer of funds from one account to another should either complete or
not happen at all
à Concurrent access by multiple users
‚ Concurrent accessed needed for performance
‚ Uncontrolled concurrent accesses can lead to inconsistencies
E g two people reading a balance and updating it at the same time
 E.g.
à Security problems
à
ƒ Database systems
y
offer solutions to all the above problems
p
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 14
Levels of Abstraction
ƒ Physical level describes how a record (e.g., customer) is stored in
a ph
physical
sical de
device.
ice
ƒ Logical level: describes data stored in database, and the
relationships among the data.
data
type customer = record
name : string;
street : string;
city : integer;
end;
ƒ View level: application programs hide details of data types.
Views can also hide information (e.g., salary) for security
purposes.
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 15
Data Independence
ƒ ability to modify a schema in one level without affecting a
schema definition in the next
ne t higher level
le el
ƒ physical data independence:
à
physical level - conceptual level
ƒ logical data independence:
à
conceptual
p
level - view level
View 1
Customer
‥‥
View n
Account
Conceptual Level
pointer or table?
Physical Level
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 16
Instances and Schemas
ƒ Similar to types and variables in programming languages
ƒ Schema – the logical structure of the database
e.g., the database consists of information about a set of customers and accounts
and the relationship
p between them))
à Analogous to type information of a variable in a program
à Physical schema: database design at the physical level
à Logical
L i l schema:
h
d t b design
database
d i att the
th logical
l i l level
l l
à
ƒ Instance – the actual content of the database at a particular
point in time
à
Analogous to the value of a variable
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 17
ƒ Scheme (schema)
à
th skeletal
the
k l t l structure
t t
off the
th data
d t content
t t
Customer
Name
Account
Address
Telephone
No
No.
Type
Balance
ƒ Instance
the actual content of the data at a given time
à database status
à
2009/3/3/12:00
Customer
2009/2/20/12:00
Customer
HS Kim
Suwon
323-3232
HS Kim
Seoul
323-3232
KS Lee
Busan
323-5454
KS Lee
Busan
323-5454
MH Choi
Seoul
553-3235
PL Park
Seoul
553-3235
KH Na
Yongin
545-5488
⋯
Original Slides:
© Silberschatz, Korth and Sudarshan
⋯
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 18
Data Models
ƒ A collection of tools for describing
ddata
t
à data relationships
à data semantics
à data constraints
à
ƒ Entity-Relationship model
ƒ Relational model
ƒ Other models:
à
à
à
object-oriented model
semi-structured data models
Older models: network model and hierarchical model
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 19
Entity-Relationship Model
Example of schema in the entity-relationship model
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 20
Entity Relationship Model (cont.)
ƒ E-R model of real world
Entities
E
titi (objects)
( bj t )
‚ E.g. customers, accounts, bank branch
à Relationships between entities
‚ E.g. Account A-101 is held by customer Johnson
‚ Relationship set depositor associates customers with accounts
à
ƒ Widely
Wid l used
d ffor ddatabase
t b design
d i
à
Database design in E-R model usually converted to design in the relational model
(coming up next) which is used for storage and processing
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 21
Relational Model
columns
ƒ Represent data in a tabular form
rows
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 22
Database Languages
ƒ Data Definition Language (DDL)
à
Used
U
d ffor ddefining
fi i DB Schema
S h
‚ create table
‚ drop column
ƒ Data Manipulation Language (DML)
à
Used for operating the data in the DB (DB instance)
‚ Retrieve
‚ Insert
‚ Delete
‚ Change
ƒ Query
a statement requesting the retrieval of information
à query language: part of DML
à sometimes “query language = DML”
à
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 23
SQL
ƒ The most widely used language
à
à
E g find the name of the customer with customer-id 192-83-7465
E.g.
select customer.customer-name
from customer
where customer.customer-id = ‘192-83-7465’
à
E.g.
g find the balances of all accounts held byy the customer with customer-id 19283-7465
à
select account.balance
from depositor, account
where depositor.customer-id = ‘192-83-7465’ and
depositor.account-number = account.account-number
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 24
Database Users
ƒ Users are differentiated by the way they expect to interact with
ƒ
ƒ
ƒ
ƒ
the system
s stem
Application programmers – interact with system through DML calls
S hi i d users – form
Sophisticated
f
requests in
i a database
d b query llanguage
Specialized users – write specialized database applications that do
nott fit into
i t the
th traditional
t diti l data
d t processing
i framework
f
k
Naïve users – invoke one of the permanent application programs
that have been written previously
à
E.g. people accessing database over the web, bank tellers, clerical staff
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 25
Database Administrator
ƒ Coordinates all the activities of the database system; the database
administrator has a good understanding
nderstanding of the enterprise’s
information resources and needs.
ƒ Database administrator's
administrator s duties include:
à
à
à
à
à
à
à
Schema definition
Storage structure and access method definition
Schema and physical organization modification
Granting user authority to access the database
Specifying integrity constraints
Acting as liaison with users
Monitoring performance and responding to changes in requirements
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 26
Transaction Management
ƒ Transaction
à a collection
ll i off operations
i
that
h performs
f
a single
i l logical
l i l function
f
i in
i a
database application
à p
programmer
g
is responsible
p
for writingg “correct” transactions
ƒ DBMS must ensure the atomicity and durability of each transaction
à atomicity : all-or-nothing
à durability : effect should be persistent
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 27
Storage Management
ƒ DBMS must effectively and efficiently manage storage (disk)
space
ƒ Storage
S
manager
à a program module
à that provides the interface
à between the low-level data stored in the database
à and the application
pp
p
programs
g
and qqueries submitted to the system
y
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 28
Data Mining & Analysis
ƒ The challenge is
“getting information out”!
Knowledge Discovery in Databases
à Extract information from the database
à
ƒ Information retrieval
Textual data files (documents)
à Find the most relevant document(s) for the given information need (query)
à
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 29
Overall
System
Structure
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 30
Application Architecture
ƒ Two-tier
Two tier architecture: E.g.
E g client programs using ODBC/JDBC to
communicate with a database
ƒ Three-tier architecture: E.g. web-based applications, and
applications
li i
built
b il using
i “middleware”
“ iddl
”
Original Slides:
© Silberschatz, Korth and Sudarshan
Intro to DB (2009-1)
Copyright © 2008 - 2009 by S.-g. Lee
Chap 1 - 31
END OF CHAPTER 1