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当前课程知识点：Database Technology and Programming >  Chapter Ⅰ Data Management Technology – Database >  1.2 Database System >  1.2.3 Three-tier Mode of Database

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1.2.3 Three-tier Mode of Database资料文件与下载

1.2.3 Three-tier Mode of Database

From a DBMS perspective, database systems usually adopt a Three-tier mode structure.

These three levels are composed of external mode, mode and internal mode.

 1. Schema

The mode is also called the logical mode, which is a description of the logical structure and characteristics of all data in the database, and is a common data view of all users. It is the middle layer of the database system, which does not involve physical storage details and hardware environment, nor is it related to specific applications and languages.

2. External Schema

The external mode is also called a subschema (Subschema), which is a description of the logical structure and characteristics of the local data that the database user can see and use, and is a data view of the database user.

External mode is a powerful measure to ensure database security. Each user can only see and access the data in the corresponding external mode, and the rest of the data in the database is not visible.

3. Internal Schema

Internal mode is also called storage mode (Storage Schema). It is a description of the physical structure and storage method of data, and a way of representing data. For example, the storage method of records is sequential storage, storage in index order, storage in B-tree structure, etc.


Mapping

In order to be able to realize the connection and conversion of three abstract levels internally, the DBMS provides two layers of images between these three levels of patterns:

• External mode / mode mapping

• Mode / intra mode mapping

It is these two layers of mapping that ensure that the data in the database system can have a high degree of logical independence and physical independence.

三级模式两级映像.png


下一节:Summary

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Database Technology and Programming课程列表：

Course Guide

-Course Guide

-Bibliography

Chapter Ⅰ Data Management Technology – Database

-From the beginning: Knowledge Point Puzzle of Chapter I

-1.1 Data & Data Management

--1.1.1 Data, Information and Databases

--PPT-1.1.1

--1.1.2 Explore Data Management

--PPT-1.1.2

-1.2 Database System

--1.2.1 DBS=DB+DBMS

--PPT-1.2.1

--1.2.2 Data Model

--PPT-1.2.2

--1.2.3 Three-tier Mode of Database

-Summary

-Exercise

-【Discussion: Will the database be replaced by blockchain? 】

Chapter Ⅱ Database Conceptual & Logical Structure Design

-Knowledge Point Puzzle of Chapter Ⅱ

-2.1 Database Design

--2.1.1 Database Design

--PPT- 2.1.1

-2.2 Conceptual Structure Design

--2.2.1 Conceptual Structure Design

--PPT- 2.2.1

-2.3 Logical Structure Design

--2.3.1 Logical Structure Design

--PPT- 2.3.1

--2.3.2 Integrity Rules of Relational Model

--PPT-2.3.2

--2.3.3 Transforming ER Model into Relational Model

--PPT-2.3.3

-Summary

-Exercise

-【Discussion: Structured data —— Relational model, Unstructured data——? 】

Chapter Ⅲ Database Physical Structure Design and Maintenance

-Knowledge Point Puzzle of Chapter Ⅲ

-3.1 Create Databases

--3.1.1 Create Databases

--PPT- 3.1.1

-3.2 Create Tables

--3.2.1 Field Type and Format

--PPT- 3.2.1

--3.2.2 Field Properties

--PPT- 3.2.2

--3.2.3 Referential Integrity

--PPT- 3.2.3

--3.2.4 Data Input

--PPT- 3.2.4

-3.3 Maintain Tables

--3.3.1 Maintain Tables

--PPT- 3.3.1

-Summary

-Exercise

-【Discussion: What is the referential integrity?】

Chapter Ⅳ Constants, Variables, Expressions, and Functions

-Knowledge Point Puzzle of Chapter Ⅳ

-4.1 Data Types, Constants and Variables

--4.1.1 Data Types, Constants and Variables

--PPT- 4.1.1

-4.2 Expressions

--4.2.1 Numeric & Character Expressions

--PPT- 4.2.1

--4.2.2 Relational & Logical Expressions, Operation Priority

--PPT- 4.2.2

-4.3 Functions

--4.3.1 Numeric Functions

--PPT- 4.3.1

--4.3.2 Character Functions

--PPT- 4.3.2

--4.3.3 Date/Time, Conversion and Iif Functions

--PPT- 4.3.3

-Summary

-Exercise

Chapter Ⅴ Data Retrieval and Query Files

-Knowledge Point Puzzle of Chapter Ⅴ

-5.1 Query and Query Files

--5.1.1 Data Retrieval Method and Query Files

--PPT- 5.1.1

-5.2 Select Query

--5.2.1 Select Query-1

--PPT- 5.2.1

--5.2.2 Select Query-2

--PPT- 5.2.2

--5.2.3 Parameter Query

--PPT- 5.2.3

-5.3 Operation Query

--5.3.1 Operation Query

--PPT- 5.3.1

-Summary

-Exercise

Chapter Ⅵ Structured Query Language - SQL

-Knowledge Point Puzzle of Chapter Ⅵ

-6.1 Summary Of SQL

--6.1.1 Summary Of SQL

--PPT- 6.1.1

-6.2 Data Definition Language

--6.2.1 SQL Definition Language

--PPT- 6.2.1

-6.3 Data Query Language

--6.3.1 Sample Query 1

--PPT- 6.3.1

--6.3.2 Sample Query 2

--PPT- 6.3.2

--6.3.3 Join Query

--PPT- 6.3.3

--6.3.4 Nested Query

--PPT- 6.3.4

--6.3.5 Group Query

--PPT- 6.3.5

-6.4 Data Manipulation Language

--6.4.1 SQL Manipulation Language

--PPT- 6.4.1

-Summary

-Exerise

Chapter Ⅶ Forms and Report Design

-Knowledge Point Puzzle of Chapter Ⅶ

-Mind Mapping

-7.1 Form Design

--7.1.1 Create a Form

--PPT- 7.1.1

--7.1.2 Form Designer

--PPT- 7.1.2

--7.1.3 Form Controls

--PPT- 7.1.3

-7.2 Report Design

--7.2.1 Report Structure and Create Report

--PPT- 7.2.1

-Summary

-Exercise

Chapter Ⅷ Structured Programming

-Knowledge Point Puzzle of Chapter Ⅷ

-8.1 VBA Programming

--8.1.1 VBA Programming Environment

--PPT- 8.1.1

-8.2 Sequence Structure

--8.2.1 Sequence Structure

--PPT- 8.2.1

-8.3 Selection Structure

--8.3.1 The “If” Statement

--PPT- 8.3.1

--8.3.2 The “Select Case” Statement & Nested Selection Structure

--PPT- 8.3.2

-8.4 Repetition Structure

--8.4.1 The “For” Statement

--PPT- 8.4.1

--8.4.2 The “Do While” Statement

--PPT- 8.4.2

--8.4.3 Nested Loop

--PPT- 8.4.3

-8.5 Functions & Procedures

--8.5.1 Functions and Procedures

--PPT- 8.5.1

--8.5.2 Parameter Transmission

--PPT- 8.5.2

--8.5.3 Variable Lifetime

--PPT- 8.5.3

-8.6 VBA Debug

--8.6.1 VBA Debug

--PPT- 8.6.1

-8.7 Arrays

--8.7.1 Define Arrays

--PPT- 8.7.1

--8.7.2 Use Arrays

--PPT- 8.7.2

-Summary

-Exercise

Chapter Ⅸ Object - Oriented Programming(OOP)

-Knowledge Point Puzzle of Chapter Ⅸ

-9.1 What is OOP？

--9.1.1 What is OOP？

--PPT- 9.1.1

--9.1.2 Objects & Classes

--PPT- 9.1.2

-9.2 Properties, Methods and Events

--9.2.1 Properties, Methods and Events

--PPT- 9.2.1

--9.2.2 Event Trigger Sequence

--PPT- 9.2.2

-9.3 OOP Examples

--9.3.1 Object Synchronization

--PPT- 9.3.1

--9.3.2 Login Interface

--PPT- 9.3.2

--9.3.3 Global Variables

--PPT- 9.3.3

--9.3.4 Connect and Access Tables

--PPT- 9.3.4

-Summary

-Exercise

Chapter Ⅹ Macro

-Knowledge Point Puzzle of Chapter Ⅹ

-Mind Mapping

-10.1 What is a Macro？

--10.1.1 What is a Macro？

--PPT- 10.1.1

--10.1.2 Commands and Classifications of Macro

--PPT- 10.1.2

-10.2 Create Macros

--10.2.1 Add New Action to a Macro

--PPT- 10.2.1

--10.2.2 Conditional Macro

--PPT- 10.2.2

--10.2.3 Macro Group

--PPT- 10.2.3

--10.2.4 Call Macro

--PPT- 10.2.4

--10.2.5 Data Macro

--PPT- 10.2.5

-10.3 Debugging and Conversion of Macro

--10.3.1 Debugging and Conversion of Macro

--PPT- 10.3.1

-Summary

-Exercise

Chapter Ⅻ Development of Desktop Database Application System

-Congradulations！Puzzle complete!

-11.1 Requirement Analysis of Database Application System

--11.1.1 System Design Process

--PPT- 11.1.1

--11.1.2 System Function Introduction

--PPT- 11.1.2

-11.2 Data Layer of Database Application System

--11.2.1 Underlying Data Structure

--PPT- 11.2.1

-11.3 Realization of Database Application System

--11.3.1 Registration and Login Module

--PPT- 11.3.1

--11.3.2 Get User Identity from Login Form

--PPT- 11.3.2

--11.3.3 Double Timer

--PPT- 11.3.3

--11.3.4 Student Client

--PPT- 11.3.4

--11.3.5 Module integration

--PPT- 11.3.5

--11.3.6 Administrator Client

--PPT- 11.3.6

-11.4 Test and Release of Database Application System

--11.4.1 Test and Release of Database Application System

--PPT- 11.4.1

-Summary

Final Exam

-Final Exam

1.2.3 Three-tier Mode of Database笔记与讨论

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