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Introduction to Database System Adisak Intana Lecturer Chapter 2: Database Architecture.

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งานนำเสนอเรื่อง: "Introduction to Database System Adisak Intana Lecturer Chapter 2: Database Architecture."— ใบสำเนางานนำเสนอ:

1 Introduction to Database System Adisak Intana Lecturer Chapter 2: Database Architecture

2 Introduction to Database System 2 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

3 Introduction to Database System 3 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

4 Introduction to Database System 4 File System A computerized data processing environment which is composed of four major parts : Hardware The computer hardware : CPU, mainmemory, and I/O devices Software – Application programs Data is in a collection of independent files Users – Naive users – Application programers

5 Introduction to Database System 5 File Processing System Environment Files Operating system Application programs

6 Introduction to Database System 6 Database system A computerized data processing environment which is composed of four major parts : Hardware The computer and the secondary storage devices Software Data is in a collection of related files in the form of database Users

7 Introduction to Database System 7 Database processing system environment Database Operating system DBMS Application program

8 Introduction to Database System 8 Database processing using DBMS Database Staff recruitmen t system Customers’ orders system Sales accounting system Departm ent2 Departm ent1 Departm ent3 Empl oyee data Produ ct data Custo mer data DB MS

9 Introduction to Database System 9 Database A shared collection of interrelated data. A collection of data stored in a standardized format and designed to be shared by multiple users. A collection of persistent related data of interest of a specific enterprize. Database contains information about a particular enterprise.

10 Introduction to Database System 10 Units of data Database 19MSasin FAmporn AgeSexNameStudent ID File Record Field Student file :

11 Introduction to Database System 11 Units of data Physical level Unit of data used by the hardware of computers. – Bit – Byte – Word

12 Introduction to Database System 12 Units of data Logical level Unit of data used or viewed by the users. – Field – Record – File – Database

13 Introduction to Database System 13 Units of data bit byte field record file database 0 or (letter K in ASCII) Amporn , Amporn, F, 18 Listing of all students in student file Student and teacher files

14 Introduction to Database System 14 Database management system (DBMS) A collection of programs that enables users to modify and extract information from a database. A suite of programs which typically manage large structured sets of persistent data and offering ad hoc query facilities to many users.

15 Introduction to Database System 15 Database users Users in database environment are people whose jobs involve the day-to-day use of large database. Users are differentiated by the way they expect to interact with the database management system. – Naive users Invoke and use the application programs that have been written for specific tasks.

16 Introduction to Database System 16 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

17 Introduction to Database System 17 Simplified view of database system User1 User2 User3 User4 User work area User work area User work area User work area Physical database Logical database Physical level Logical level Externalal level

18 Introduction to Database System 18 External level เป็นสถาปัตยกรรมข้อมูลระดับนอก สุด ใกล้ชิดกับผู้ใช้ฐานข้อมูลมาก ที่สุด เพราะเป็นระดับที่กล่าวถึง มุมมองข้อมูลของผู้ใช้แต่ละคน (user view) ผู้ที่เกี่ยวข้องคือ user ที่ใช้ฐานข้อมูล

19 Introduction to Database System 19 Logical level เป็นสถาปัตยกรรมข้อมูลระดับที่ อยู่ระหว่าง Internal กับ External ทำหน้าที่ถ่ายทอด รูปแบบของ Physical Level ให้ อยู่ในรูปแบบที่สามารถเข้าใจได้ ง่าย (Logical Structure) ผู้ที่ เกี่ยวข้องกับข้อมูลในระดับนี้คือ DBA

20 Introduction to Database System 20 Physical level เป็นสถาปัตยกรรมฐานข้อมูลระดับในสุด ซึ่งอธิบายโครงสร้างของการจัดเก็บ ข้อมูลในเชิงกายภาพ (Physical Structure) ผู้ที่เกี่ยวข้องกับระดับนี้คือ DBA และ System Administrator

21 Introduction to Database System 21 Example สถาปัตยกรรมระบบฐานข้อมูลทั้ง 3 ระดับ สามารถ อธิบายได้โดยใช้ ฐานข้อมูลระบบงานสินค้าคงคลัง (northwind) ดังนี้ Physical Level – ฐานข้อมูล Northwind เก็บอยู่ในไฟล์ที่ชื่อว่า northwind.mdb ซึ่งเป็นไฟล์ของโปรแกรม MS Access – ทำงานอยู่บนระบบปฏิบัติการ MS Windows 95/98 – เก็บอยู่ใน directory c:\program files\microsoft office\samples บน Hard Disk ณ ตำแหน่ง Sector 84A6, Track 15, Cylinder 8 เป็นต้น

22 Introduction to Database System 22 Example External Level ฐานข้อมูล Northwind แบ่งให้ พนักงานแผนกต่าง ๆ มองเห็นได้ต่างกัน ดังนี้คือ – พนักงานฝ่ายขาย มองเห็นข้อมูลใน Caregories, Orders, Order Details, Products, Categories – พนักงานฝ่ายบุคคล มองเห็นข้อมูลใน Employees, Orders – ผู้จัดการทั่วไป (GM) มองเห็นข้อมูลทั้งหมด

23 Introduction to Database System 23 Example Logical Level ฐานข้อมูล Northwind ประกอบด้วย – Tables คือ Categories, Customers, Employees, Order Details, Orders, Products, Shippers และ Suppliers – Queries คือ Category Sales for 1995, Current Product List, Employee Sales by Country,

24 Introduction to Database System 24 Simplified view of database system DBA(s)/Programmers/Naive users Programs/Query Processor Programs to access stored data Data dictionary Users’ database Programs/Query Language

25 Introduction to Database System 25 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

26 Introduction to Database System 26 Database users – Application programmers Write application programs and interact DBMS through database language. – Database administrator

27 Introduction to Database System 27 Database administrator Responsible for all the activities of the database system environment. Must have a good understanding of the enterprise’s information resources and needs.

28 Introduction to Database System 28 Database administrator Database administrator's duties include : – Define the schema – Define storage structure and access method – Modify schema and physical organization – Granting user authority to access the database – Specifying integrity constraints – Acting as liaison with users – Monitoring performance and responding to changes in requirements

29 Introduction to Database System 29 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

30 Introduction to Database System 30 Database independence The ability to change the description of a database structure at one level of the database system architecture without having to change the description at the next higher level database structure.

31 Introduction to Database System 31 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

32 Introduction to Database System 32 Data dictionary The data dictionary or system catalog contains metadata Metadata means “data about the data” This metadata is the definitions of the structure, data type, integrity constraints, etc. of the database and other objects in the DBMS rather than the users’ raw data.

33 Introduction to Database System 33 Data dictionary The data dictionary can be regarded as a database in its own right, but it is the system database rather than user database. The data in the data dictionary should be integrated into a database with the same structure as the user database. It should certainly be possible to query the data dictionary just like the users’ database.

34 Introduction to Database System 34 Example Data dictionary

35 Introduction to Database System 35 Example Data in Database

36 Introduction to Database System 36 Table Contents Database system environment Database system architecture Database users Data independence Data dictionary Advantages and disavantages of database system

37 Introduction to Database System 37 Advantages of database approach u Providing a solution to basic data storage and retrieval. u Providing flexibility and availability of up-to- minute information. u Reducing data redundancy. u Obtaining data consistency. u Sharing of data.

38 Introduction to Database System 38 Advantages of database approach (continue) u Standard can be enforced. u Ad hoc queries are possible. u Ease of application programs development. u Reduce application program development time. u Uniform security, privacy, and integrity can be applied. u Obtaining data independence.

39 Introduction to Database System 39 Disadvantages of database approach High cost – Conversion from file processing to DBMS – More sophisticated hardware and software – Higher operating costs (personnel) Complexity of DBMS administration Vulnerability to failure Difficulty of recovering & securing data assets


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