Ch. 1 데이터베이스시스템

What to Learn

     

Database System Overview

Entity-Relationship diagram Relational Data Model   SQL language How to use Commercial DBMS ’ s  Structure & Constraints MS Access  MS SQL Server Normalization (정규화) Transaction & Concurrency (동시성) Ch.1 Database System 데이터베이스시스템 2

What to Learn

 Database and Database system  Modeling a real world    Conceptual Modeling Data Modeling Data Structuring  File processing system  Advantages of database system Ch.1 Database System 데이터베이스시스템 3

What is a database (1)

  data numbers, characters, images or other outputs from devices to convert physical quantities into symbols, in a very broad sense 현실세계의 사물과 사건을 문자, 수치, 기호, 음성, 그 림 등의 형태로 표현한 기록 (record) information the result of processing, manipulating and organizing data in a way that adds to the knowledge of the person receiving it. 사용자에게 전달되어 의사결정 등에 유용하게 쓰이도 록 가치 있는 형태로 변환된 뜻(meaning, interpretation) Information = Processing (Data) Ch.1 Database System 데이터베이스시스템 4

What is a database (2)

  database a collection of persistent data that is used by the application systems of some given enterprise 체계적으로 저장되고 통합적으로 관리되는 데이터의 집합 (collection) Textbook definition (p.13) 조직체의 응용시스템들이 공유해서 사용하는 운영데 이터(operational data)들이 구조적으로 통합된 모임 (operational data means data from day-to-day operations. In these days we store all the necessary data in the database including decision support database, not just operational data) Ch.1 Database System 데이터베이스시스템 5

Database system

 Database system computerized record – keeping system a computerized system whose overall purpose is to store information and to allow users to retrieve and update that information on demand.

데이터베이스 개념과 기술에 입각하여 데이터를 수집/저 장/가공/제공하는 컴퓨터 응용시스템  Database Management System (DBMS) A component of a database system Software that handles all access to the database Ch.1 Database System 데이터베이스시스템 6

Database system

Information Processing Users DBMS Computer Database Ch.1 Database System 데이터베이스시스템 7

Modeling of the Real World

Real World system boundary conceptual modeling E-R diagram data modeling conceptual world logical schema data structuring physical schema stored database computer world Ch.1 Database System 데이터베이스시스템 8

Conceptual modeling

  System boundary only the data we are interested in Entity  any distinguishable object that is to be represented in the database e.g. book, student, department Relationship an association among entities Ch.1 Database System 데이터베이스시스템 9

E-R diagram

Publisher publish Book loan Student title belong Seller purchase author ISBN loan date return date   purchase date Department Attributes (properties 속성) Items we describe (express) entities or relationships with From the view of a database, entities and relationships are the same both of them are represented as tables Ch.1 Database System 데이터베이스시스템 10

Data Modeling

  Data model an abstract, self-contained, logical definition of the objects, operators, constraints, and so forth, that together constitute the abstract machine 가상의 컴퓨터에서 데이터 객체들 의 구조, 연산, 제약조건들을 명시 한 정의 Data models differ in structure, operators, constraints Ch.1 Database System 데이터베이스시스템 11

hierarchical data model (p.35)

회사 부서1 부서1 프로젝트1 사원1 사원2 프로젝트2 사원3 사원4 프로젝트3 사원5    pre-relational, tree-structure, use pointers a node has only one parent node What if an employee works for two projects Ch.1 Database System 데이터베이스시스템 12

network data model (p.36)

대학 학과1 학과2 과목1 학생1 학생2 과목2 학생3 학생4 과목3 학생5   pre-relational, use pointers a node can have more than one parent node Ch.1 Database System 데이터베이스시스템 13

relational data model

 Student table NAME 송치윤 김구완 최재석 조미림 ST_NO 52015 53116 56034 52042 ADDRESS 사당동 홍제동 양재동 역삼동 DEPT 컴퓨터 정보통신 정보관리 컴퓨터 GRADE 3.3

3.1

3.5

2.9

 The data is perceived by the user as tables (and nothing but tables) 데이터베이스의 논리적 구조가 relation 즉, 테이블의 집합으로 표현 되는 데이터 모델 relation is a mathematical term for a table Ch.1 Database System 데이터베이스시스템 14

Other data model

 Object-oriented data model from the OOP (object oriented programming) use pointers  Object/Relational data model hybrid of OODB & RDB Ch.1 Database System 데이터베이스시스템 15

Data Structuring

   Physical representation of data Consider file structure indexing Ch.1 Database System 데이터베이스시스템 16

file processing system vs. database system

 What is file processing system  Which is easier to use?

 Problems of file processing system 1. data incompatiblity 2. data redundancy 3. data dependency Ch.1 Database System 데이터베이스시스템 17

example of problems

Product1 (Prod_No, Prod_Name, price, monthlysales) Product2 (Prod_No, Prod_Name, cost, monthlyproduction)     Product1 is sorted by Prod_No, while Product2 is sorted by Prod_Name Sales department & production department use different names for the same product.

Prod_Name ’ s are used twice If the cost is inserted in Product1, application program that used Product1 should be changed.

Ch.1 Database System 데이터베이스시스템 18

Data in the database system

 Shared by multi-users  Integrated in a single database  Above characteristic requires     Standardization (표준화) Concurrency control (동시성 제어) Integrity (무결성) Security (보안성) Ch.1 Database System 데이터베이스시스템 19

Advantages of database systems

 The data can be shared  Redundancy and Incompatibility can be reduced  Transaction support can be provided (Transaction Commit or Rollback)  Integrity can be maintained  Security can be enforced  Standards can be enforced  Conflicting requirements can be balanced Ch.1 Database System 데이터베이스시스템 20