Lecture 1.2

Dept. of Information Systems Hanyang University

Slide Reference: fundamentals of database systems, pearson

Outline

• Introduction

• An Example

• Characteristics of the Database Approach

• Actors on the Scene

여기 밑에는 ppt에 없음.

• Workers behind the Scene

• Advantages of Using the DBMS Approach

• A Brief History of Database Applications

Overview

• Traditional database applications

  • Store textual or numeric information

• Multimedia databases

  • Store images, audio clips, and video streams digitally

Uses of Databases

• Data warehouses and online analytical processing (OLAP) systems

  • Extract and analyze useful business information from very large databases

  • Support decision making

• Real-time and active database technology

  • Control industrial and manufacturing processes

Introduction

Basic Chacteristics and Components of DB

Database

Collection of related data

• Known facts that can be recorded and that have implicit meaning

• Miniworld or universe of discourse (UoD)

  • ??

• Represents some aspect of the real world

• Logically coherent collection of data with inherent meaning

• Built for a specific purpose

Example of a large commercial database

• Amazon.com

Database management system (DBMS)

• Collection of programs

• Enables users to create and maintain a database

Defining a database

• Specify the data types, structures, and constraints of the data to be stored

• https://www.oracle.com/database/what-is- database.html

Meta-data

• Database definition or descriptive information

• Stored by the DBMS in the form of a database catalog or dictionary

Manipulating a database

• Query and update the database miniworld

• Generate reports

Sharing a database

• Allow multiple users and programs to access the database simultaneously

Application program

• Accesses database by sending queries to DBMS

Query

• Causes some data to be retrieved

Transaction

• May cause some data to be read and some data to be written into the database

Protection includes:

• System protection
• Security protection

Maintain the database system

• Allow the system to evolve as requirements change over time

Figure 1.1

위의 내용들을 총정리한 그림

An Example

UNIVERSITY database

Information concerning students, courses, and grades in a university environment

• Data records

  • STUDENT

  • COURSE

  • SECTION

  • GRADE_REPORT

  • PREREQUISITE

Specify structure of records of each file by specifying data type for each data element

• String of alphabetic characters
• Integer

Construct UNIVERSITY database

Store data to represent each student, course, section, grade report, and prerequisite as a record in appropriate file

• Relationships among the records

• Manipulation involves querying and updating

Examples of queries:

• Retrieve the transcript

• List the names of students who took the section of the ｀Database¨ course offered in fall 2020 and their grades in that section

  • sql로 이 명령문을 바꾸기 혹은 sql을 읽고 의미가 뭔지 해석하는 문항 나올 수 있다.

• List the prerequisites of the ｀Database¨ course

Examples of updates:

• Change the class of ｀Smith¨ to sophomore

• Create a new section for the ｀Database¨ course for this semester

• Enter a grade of ｀A¨ for ｀Smith¨ in the ｀Database¨ section of last semester

Phases for designing a database:

• Requirements specification and analysis

• Conceptual design

• Logical design

• Physical design

Characteristics of the Database Approach

• Traditional file processing

  • Each user defines and implements the files needed for a specific software application

• Database approach

  • Single repository maintains data that is defined once and then accessed by various users

• Main characteristics of database approach

  • Self-describing nature of a database system

  • Insulation between programs and data, and data abstraction

  • Support of multiple views of the data

  • Sharing of data and multiuser transaction processing

Self-Describing Nature of a Database System

• Database system contains complete definition of structure and constraints

Meta-data

Describes structure of the database

• Database catalog used by:

  • DBMS software

  • Database users who need information about database structure

Insulation Between Programs and Data

• Program-data independence

  • Structure of data files is stored in DBMS catalog separately from access programs

• Program-operation independence

  • Operations specified in two parts:

    • Interface includes operation name and data types of its arguments

    • Implementation can be changed without affecting the interface

Data Abstraction

Allows program-data independence and program-operation independence

• Conceptual representation of data

  • Does not include details of how data is stored or how operations are implemented

• Data model

  • Type of data abstraction used to provide conceptual representation

여기 밑에서부터는 별로 비중있게 수업 x

Support of Multiple Views of the Data

View

Subset of the database, Contains virtual data derived from the database files but is not explicitly stored

Multiuser DBMS

Users have a variety of distinct applications

• Must provide facilities for defining multiple views

Sharing of Data and Multiuser Transaction Processing

• Allow multiple users to access the database at the same time

Concurrency control software

• Ensure that several users trying to update the same data do so in a controlled manner

  • Result of the updates is correct

• Online transaction processing (OLTP) application

Transaction

• Central to many database applications

• Executing program or process that includes one or more database

Isolation property

Each transaction appears to execute in isolation from other transactions

Atomicity property

Either all the database operations in a transaction are executed or none are

Actors on the Scene

Database administrators (DBA) are responsible for:

• Authorizing access to the database

• Coordinating and monitoring its use

• Acquiring software and hardware resources

Database designers are responsible for:

• Identifying the data to be stored

• Choosing appropriate structures to represent and store this data

End users

• People whose jobs require access to the database

Types

• Casual end users

• Naive or parametric end users

• Sophisticated end users

• Standalone users

System analysts

• Determine requirements of end users

• Application programmers

• Implement these specifications as programs