chapter 1 introduction l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 1 Introduction PowerPoint Presentation
Download Presentation
Chapter 1 Introduction

Loading in 2 Seconds...

play fullscreen
1 / 15

Chapter 1 Introduction - PowerPoint PPT Presentation


  • 93 Views
  • Uploaded on

Chapter 1 Introduction. Basic Concepts of Database Systems. Database is A collection of data organized in some way grouped on what they refer to, or on technical types relationships between pieces of data determined

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 1 Introduction' - dick


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 1 introduction
Chapter 1

Introduction

basic concepts of database systems
Basic Concepts of Database Systems
  • Database is
    • A collection of data organized in some way
      • grouped on what they refer to, or on technical types
      • relationships between pieces of data determined
  • Data = symbols for recording and communication (e.g., customer ID and name)
  • Example: Think of records (paper, electronic) describing employees.
    • The organization of data can be explained by metadata.
  • Metadata define how data are organized (e.g., Employee is a class of data, which has x number of attributes, and each attribute belongs to a data type).

EmployeeID Number

LastName Text

FirstName Text

Phone Number

More 

basic concepts
Basic Concepts
  • Database Management System (DBMS)
    • Software for creating databases, storing & retrieving data, creating user interface (forms), creating reports, and administering a DB system (security, access, etc.).
  • DBMS Product (a specific DBMS software; same as “DBMS Brand”).
  • Database System (DBMS Application, Application)*:
    • An implementation of a DBMS product including one or more databases, logic (business rules), some code, and user interface.
      • Supporting various information needs.
    • An information system that results from “applying” a DBMS or a database.
      • Supporting specific information needs.
file processing systems vs db systems dbs
File (Processing) Systems vs. DB systems (DBS)
  • History but also frequent shortcut today (e.g., Excel as surrogate of DBS)
  • File Processing Systems:
    • Data files and program files (code) that work on data files, or
    • Data and code in the same file
  • Must have code (programs) for data input, modification, retrieval, & deletion.
  • Data files are closely coupled with programs that define metadata - tight coupling reducing design flexibility (changes).

More 

file processing systems vs db systems
File (Processing) Systems vs. DB systems

DBS are:

  • Higher on retrieval capabilities
  • Lower redundancy, higher data integrity
  • Data independent from programs (code); looser coupling –

changes in data and code less restricted

  • Better security and management of concurrent access to database
  • Significantly lower development and maintenance cost
  • But keep in mind: Excel’s enduring popularity in companies.
modifying data in dbs data program independence
Add cell tel. number to employee table

Open table template

Add data element

Existing reports, queries, code will not crash although need to be modified to output new data – looser coupling

Modifying Data in DBS-- Data-Program independence

Field Name Data Type Description

EmployeeID Number Autonumber..

TaxpayerID Text Federal ID

LastName Text

FirstName Text

. . .

Phone Text Phone Number

. . .

CellPhone Text Cell Phone No.

db system components

D B M S

DB System Components

Database

Database Engine:

  • CRUD* operations & Data Dictionary
  • Concurrency & Lock Manager
  • Recovery Manager
  • Disk Space Manager

Data & Metadata

Management

Security

Management

Query Processor

Retrieval

Form

Builder

Report

Writer

Input/Output;

User Interface

Application

Generator

System development

tools

*CRUD= Create, Read, Update, Delete

Note: The Post book mixes “database” With “data” and “application”.

creating outputs via report writer

Query Processor

2

Creating Outputs via Report Writer

Database

4

3

Database Engine

5

Report Writer

1

6

Output: Report

relational database standard
Relational Database Standard
  • “Relation” = table, a logical view of the data

structure for storing data.

An example of Table (Sale) created in Oracle.

examples of relational dbms products
Examples of Relational DBMS Products
  • Oracle
  • Sybase
  • Informix (Unix)
  • DB2, SQL/DS (IBM)
  • Access, SQL Server (Microsoft)
  • Older (IMS, Focus)
  • Many limited to PC (MS Access, dBASE, Paradox, …)
  • Open source: MySQL (more)
hierarchical database

Customers

files

Entry point

Customer

XYZ

pointers

Order 2

Order 1

Order

files

pointers

Item C

Item B

Item A

Item A

To retrieve how many of item A are sold, start at the top from Customer. Then all nested data are retrieved top-down and left-right.

Different data models needed for different retrieval tasks (e.g., Order at the root) =>

high data redundancy in DBS!

Items

Item# ItemName Quantity

998 Dog Food 12

764 Cat Food 11

Hierarchical Database
  • First commercial standard (IBM’s IMS)
  • Still used (legacy systems)
network database

Entry point

Customer

XYZ

Order 1

Order 2

Entry points

Item C

Item B

Item A

Network Database

Relationships between records also

supported by pointers;

complex programming.

One data model supports different retrieval paths (by

customer, order, item).

relational database
Relational Database

Foreign Key (FK)

Primary Key (PK, Key)

Customer(CustomerID, Name, …)

Order(OrderID, CustomerID, OrderDate, …)

ItemOrdered(OrderID, ItemID, Quantity, …)

Item(ItemID, Description, Price, …)

  • Data organized as logical tables, consisted of rows (records) and columns (attributes), and connected via key attributes.
  • Possible to retrieve almost any combination of rows and columns, and a specific piece of data (field) within a row.
  • Pointers transparent to developers, just need to specify Key—Foreign Key relationships.
object oriented databases

Order

Customer

OrderID

CustomerID

CustomerID

Name

Government

Customer

Commercial

ContactName

ContactPhone

Discount, …

NewOrder

DeleteOrder

Add Customer

Drop Customer

Change Address

ContactName

ContactPhone

NewContact

AddNewContact

Data

Procedures (behavior,

methods) for processing

data.

Generalization/Specialization

supported;inheritance

Object-Oriented Databases
object relational db systems
Object-Relational DB Systems
  • More frequent than pure object-oriented systems
  • Architecture:
    • Database is relational
    • Objects are created in main memory according to class diagram and business rules, and populated by data from the relational databases (data access layer in system sequence diagrams)
    • System operations, then, performed by objects