Midterm Review - Database Management and Design - Lecture Slides, Slides of Introduction to Database Management Systems

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Outlines

1. Database Concepts
2. Relational Database
3. Object-oriented Database
4. Entity-Relationship Diagram
5. Unified Modeling Language
6. Normalization

1. Database concepts

• Data vs. Information
• Data vs. Database
• DBMS vs. Database system
• Level of abstraction
• Data independence
• Different database models
• Architecture of database system

Data vs. Database

• Database is a collection of related data
• Database stores data in an organized manner (i.e. minimal data redundancy)
• Database exists, first and the foremost, to serve users’ requirements

DBMS vs. DB system

• DBMS allows users to access data (i.e. interface between users and database)
• DB system is composed of DBMS, people, database, and procedures

Level of abstraction

• Conceptual : independent of s/w and h/w
  • How humans see the world
• Logical : s/w dependent
  • How programs see the world
• Physical : h/w dependent
  • How machines see the world

Real-world view

Machine code

Abstract

Concrete

Data independence

• Separation of program from data
• Program’s ability to retrieve data without changing the structure of code
• Logical data independence
  • Program’s ability to retrieve data without changing the structure of s/w-specific code
  • When a system uses 4GL language (or non-procedural language)
• Physical data independence
  • Program’s ability to retrieve data without changing the structure of h/w-specific code
  • When a system uses <= 3GL language (or procedural language)

Hierarchical DB model

• The world is represented with tree-like structure
• Only one-to-many relationships (i.e. parent-child relationship) are allowed
• Relationships between entities are built through reference point (e.g. pointer)
• Logical data independence (yes)
• Physical data independence (no)

Network DB model

• The world is represented with web-like structure
• Many-to-many relationships are allowed
• Relationships between entities are built through reference point (e.g. pointer)
• Logical data independence (yes)
• Physical data independence (no)

Object-oriented DB model

• The world is represented with a collection of objects
• Object embeds attribute, operation and relationships
• Complex objects can be represented through abstract data type
• Embody OO concepts such as encapsulation, inheritance and polymorphism

Architecture of DB system

1. External view user’s view, local (incomplete)
2. Conceptual/logical view designer’s view, global
3. Internal view Programmer’s view

• Physical view Implementation view, contains most details
• Organized by level of abstraction
• Data independence is embodied by the proper separation between four layers

Representation

• The world are viewed as entities and relationships
• Entities are modeled as table
• Relationships are built through common attributes between entities

Table

• Row represents a single entity
• Column represents attribute
• Cell represents a single value in the intersection between row and column

Integrity rules

• Entity integrity
  • Each entity (record) must be uniquely identified (by primary key: PK)
  • PK should be Not Null for entity integrity to be enforced
• Referential integrity
  • One table must reference another table properly (by foreign key: FK)
  • FK should be Not Null for referential integrity to be enforced

Relationships

• M:N

• Yields data redundancy
• Composite (or bridge) entities are needed to transform into 1:M