Introduction [2]

Information Systems (IS)

• Collection
• Organization
• Storage
• Access
• Usage

Computerized IS

• part of overall Information System

Information Base Spectrum

• Airline Reservations
• Banking Records
• Computerized Library with structured or text access
• Computerized Maps
• Medication Advisor

Introduction: Databases [3]

Information Management Technology

• Database Management
  • supports access to collections of structured/formatted data
• Information Retrieval
  • stresses keyword and full-text processing and retrieval
• Knowledge Representation
  • oriented to the capture of a wide variety and depth of meaning

Database

• a collection of highly structured data
• along with a set of access and control mechanisms

Database System

• software (and possibly hardware) system supporting a database

Introduction: Database Goals [4]

• provide users with a meaning-based view of the data
• shield from irrelevant detail
• support operations on the data
• control the data
  • integrity
  • protection
  • concurrency
  • recovery
• support sharing of different databases and users
• operate efficiently
• support evolution

Introduction: Health Insurance Example [5]

• centered around
  • subscribers
  • groups
  • claims
  • providers
• activities include
  • new subscribers
  • removal of subscribers
  • group organization
  • change of coverage
  • record payments of claims, premiums
• structured data
• data-intensive manipulations
• many users
• varied users

Introduction: Variety of Users [6]

• various levels of computer and database expertise
• varied degrees of application environment knowledge
  • programmers
  • department managers
  • clerks
  • claim adjusters
  • underwriters
  • actuaries
  • auditors
• different needs (views of the data)
• avoid having to know more than necessary

Introduction: DBMS [7]

Data Independence

• user view
  • semantically expressive
  • implementation independent
• implementation view, physical implementation

Separation critical for evolution of database

Database Management System (DBMS)

• intended for use in a variety of application environments
• software system that provides common, controlled approach
  • data organization/storage/control/access
• usually distinquished by Data Dictionary
  • set of files to describe the structure or schema
  • symbolic access to data items

Introduction: DBMS [8]

Tailored Database System (DBS) vs DBMS

``You can pay me now, or you can pay me later.''

• DBS: can tailor to suit application
• DBS: optimized performance
• DBMS: off-the-self capability
• DBMS: standardization
• DBMS: higher level of abstraction

Introduction: Architecture [9]

User View ... User View

$\searrow \swarrow$

Logical/Conceptual Level

$\downarrow$

Physical Database Organization

$\downarrow$

Operating System and Hardware

Introduction: Logical Level [10]

• provide users with abstract, logical view
  • physical realization is hidden
• Database Model
  • collection of logical data structures (tables, trees, etc.)
  • operations for manipulating those structures
• Schema
  • description of a specific database in terms of a database model
• Instance
  • current content or assignment according to the schema

Introduction: Database Models [11]

• relational
  • data in ``tables''
  • simple structure
  • uniform representation
  • simple update operations
  • simple, high-level, powerful query
• hierarchical
  • data in ``trees''
  • works well if data is truly hierarchical
  • more complicated operations
  • must specify path for query
• network
  • data in ``graphs''
  • more flexible than hierarchical
  • complex navigation for query
• others

Outline [12]

database

• computerized storage of data

relation

• data is stored in flat tables

outline

A

Relational Model

B

Relational Operators

C

SQL Select

D

QBE

E

Example Queries

F

Data Dictionary

G

SQL Features