DATABASE

1. CHAPTER 1

1.1. Database Schema

1.1.1. External Schema

1.1.1.1. User views

1.1.1.2. Subsets of concetual schema

1.1.1.3. Determined from **business-function/data entity matrices**

1.1.1.4. DBA determines schema for different users

1.2. Disadvantages of file processing

1.2.1. Program-Data Dependence

1.2.1.1. maintain metadata for each file

1.2.2. Duplication

1.2.2.1. copies same data

1.3. Problems with data dependency

1.3.1. waste of space

1.3.2. more maintain

1.3.3. biggest problem

1.3.3.1. inconsistencies (khong nhat quan)

1.3.3.2. conpromises in data integrity

1.4. Elements of the database approach

1.4.1. Data models

1.4.1.1. Graphical

1.4.1.1.1. Enterprise Data Model

1.4.1.1.2. Project Data Model

1.4.2. Entities

1.4.2.1. tap hop cac thuoc tinh (composed of attributes)

1.4.2.2. Noun form (person, place, object, event, concept)

1.4.3. Relationships

1.4.3.1. between entities

1.4.3.2. usually 1:M, M:N, 1:1

1.4.4. Relational Database

1.4.4.1. table (relations) + primary/ foreign key

1.5. Components of the database enviroment

1.5.1. Data modeling and design tools

1.5.2. Repository

1.5.2.1. centralized **storehouse ** of **metadata**

1.5.3. Database Management System (DBMS)

1.5.3.1. software for **managing ** the **database**

1.5.4. Database

1.5.4.1. **storehouse** of the **data**

1.5.5. Application Programs

1.5.5.1. software using the data

1.5.6. User Interface

1.5.6.1. text, graphical displays, menus, etc. for user

1.5.7. Data/Database Administrators

1.5.7.1. responsible for maintaining the database

1.5.8. System Developers

1.5.8.1. personnel responsible for designing databases and software

1.5.9. End Users

2. CHAPTER 2

2.1. ER model constructs

2.1.1. Entities

2.1.1.1. Entity instance

2.1.1.1.1. people, event, concept,

2.1.1.1.2. row in a table

2.1.1.2. Entity type

2.1.1.2.1. collection of entities

2.1.1.2.2. a table

2.1.2. Relationships

2.1.2.1. Relationship instance

2.1.2.1.1. link between entities

2.1.2.1.2. primary key/ foreign key in related table

2.1.2.2. Relationship type

2.1.2.2.1. link between entities type

2.1.2.2.2. phan loai giua 2 entities type voi nhau

2.1.2.3. Attributes (properties)

2.1.2.3.1. field in a table

2.1.3. Data definition

2.1.3.1. Term

2.1.3.1.1. word or phrase with **specific meaning**

2.1.3.2. Fact

2.1.3.2.1. association between two or **more term**

2.1.4. Guidlines for good data definition

2.1.4.1. concsie description (mo ta ngan gon)

2.1.4.2. Gathered in conjunction with systems requirements

2.1.4.3. accompanied by diagrams (kem theo so do)

2.1.4.4. consensus (dong thuan), iteratively refined (tinh chinh lap di lap lai)

2.1.5. Entities

2.1.5.1. Entity

2.1.5.1.1. person, place, object, event orr concept

2.1.5.2. Entity type

2.1.5.2.1. **collection of entites** share common **properties or characteristics**

2.1.5.3. Entity instance

2.1.5.3.1. a single occurrence

2.2. Modeling relationships

2.2.1. associative entity

2.2.1.1. combination of relationship and entities