Download Chap0. Background - Internet Database Lab.

Chap 0. Background
서울대학교 컴퓨터공학부
객체지향시스템연구실
(SNU-OOPSLA-LAB)
김 형주 교수
File Structures
SNU-OOPSLA Lab.
1
Contents
Contents
 Database
Definitions
 Database
Organizations
 DBMS
 Why
File Structures?
 Basic
File Structures
Trend
File Concepts
SNU-OOPSLA Lab.
2
Database Definitions
Database Definitions

One definition - anything conceivably useful in
collecting, using, maintaing, or managing data

Webster’s Ninth New Collegiate Dictionary defines
“a collection of data organized especially for rapid
search and retrieval(as by computer)”

In addition to these, these are many definitions of
“DataBase”

The common thread all of these definitions is data
organization and easy retrieval
File Structures
SNU-OOPSLA Lab.
3
Database Organization
Database Organization(1)


The organization of a database affects

the way the actual data is stored

what types of data operations are possible

the ease or difficulty of expressing requests (queries)
The organization even affects the way you think
about your data
File Structures
SNU-OOPSLA Lab.
4
Database Organization
Database Organization(2)

Traditionally there has been 3 ways of database
reorganizations


Hierarchical database organization

Network database organization

Relational database organization
Nowadays

Object-oriented database organization

Object-relational database organizaton
File Structures
SNU-OOPSLA Lab.
5
DBMS Status
DBMS Trend

70년 대 : Network & Hierarchical DBMS

80년 대 : Relational DBMS

90년 대 : RDBMS 확장형, Object-Oriented DBMS

98년 이후: Object-Relational DBMS

2000년 대 : Next-Generation DBMS

Multimedia, Intelligence, WEB support
File Structures
SNU-OOPSLA Lab.
6
Why File Structures
Why File Structures?
Data Intensive Application
Data Intensive Application
DBMS
File System
Query, Transaction
Storage Engine
File Management
File Management
Operating
System
Operating
System
File Structures
SNU-OOPSLA Lab.
7
Basic File Concepts
Basic File Concepts(1)
 Entity
& Attributes
 Entity
: data object
 Attributes
: charaters of the entity
e.g. employee = (name, address, id_number, department, ...)
 Data
field, data item
 Information
is not data
Processing
Data
File Structures
Information
SNU-OOPSLA Lab.
8
Basic File Concepts
Basic File Concepts(2)

Records

Record : method of storing an entity using fields collection of
data values that describes an entity
record employee =
name : array [1..30] of char;
address : array [1..40] of char;
id : array [1..9] of char;
dept : (executive, management, sales,
research, support)
salary : integer;
end


Record type
Record instance (= record occurrence)
File Structures
SNU-OOPSLA Lab.
9
Basic File Concepts
Basic File Concepts(3)

Fixed-length record
Name
30bytes

Address
40bytes
Id
Dept
9bytes
integer
Salary
integer
Variable-length record

Variable length fields
Name
Address
30bytes
40bytes
Name
Address
30bytes
25bytes
File Structures
Id
Dept
9bytes
integer
Id
9bytes
SNU-OOPSLA Lab.
Dept
integer
Salary
integer
Salary
integer
10
Basic File Concepts
Basic File Concepts(4)
 variable
format records : Pascal’s variant
records(e.g. hourly, monthly, yearly salary)
Type=“S”
Name
Address
Id
Dept
Salary
Monthly Rate
Type=“H”
Name
Address
Id
Dept
Salary
Hourly Rate
 repeating
Name
Emp
Nbr
File Structures
Hours Worked
groups : multiply occurring fields
Insurance
Type
Dependent
Name
Dependent
BirthDate
SNU-OOPSLA Lab.
Dependent
Name
Dependent
BirthDate
. . .
11
Basic File Concepts
Basic File Concepts(5)

Key

Keys : attributes to select or order records within a file

Primary keys : should uniquely distingush the records; often
basis for ordering records physically within a file

e.g. employee id # or vehicle id # or ju-min #

Secondary key : e.g. name to access alphabetically, dept-name

External key : artificially assigned, record number within
file, independent of attributes values
File Structures
SNU-OOPSLA Lab.
12
Basic File Concepts
Basic File Concepts(6)
 File
 File
: group of all records representing entities of
the same type collecting of records about similar
entities
 File Structure : A method of structuring (or
organizing) records of a file on secondary
storage device
 Data Structure : A method of structuring (or
organizing) records of a file on main memory
Continued..
File Structures
SNU-OOPSLA Lab.
13
Basic File Concepts
Basic File Concepts(6)

Phsical database : A collection of inter-connected file structures;
an implementation of a logical database
Ford Fairmont AB789 V6
Honda Accord QXJ55 V4
Buick Regal
A21M V8

silver
red
red
1978
1988
1982
Why use file concept?

Data set is too large to store all in main memory

Program access part of all data set in specific time

To keep data independence (it can be shared by application
program)
File Structures
SNU-OOPSLA Lab.
14
Basic File Concepts
Basic File Concepts(7)
 Classification
 By
function

master file

transaction file

report file

work file

program file
 By
File Structures
of File
access type of program

input file

output file

input/output file
SNU-OOPSLA Lab.
Continued..
15
Basic File Concepts
Basic File Concepts(8)
 Classification
 By
File Structures
of File(Continued)
organizing method

sequential file

B-Tree file

Hashing file

Grid file
SNU-OOPSLA Lab.
16
Contents
LET’S REVIEW!!
 Database
Definitions
 Database
Organizations
 DBMS
 Why
File Structures?
 Basic
File Structures
Trend
File Concepts
SNU-OOPSLA Lab.
17