Introduction to Database Management System

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Introduction to Database Management System
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Data vs. Information

• Data
• Raw facts, text, graphics, images, sound and
  video segments that have meaning in the users
  environment
• Information
• Data that have been processed in such a way as to
  increase the knowledge of the person who uses the
  data
• Data are raw facts. Information is processed data
  to reveal the meaning behind the facts.

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Traditional Approach

• Systems used files to store information
• Separate systems - Separate files and programs
  for each application
• E.g. Payroll files, Personnel files, Accounts
  files etc.

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Example of file system
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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)

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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)
• wasteful of space (storage)

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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)
• wasteful of space (storage)
• update inefficiencies

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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)
• wasteful of space (storage)
• update inefficiencies
• (when a teacher moves to a new address, or
  changes her name, the teacher's "record" must be
  changed each place it is stored)

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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)
• wasteful of space (storage)
• update inefficiencies
• (when a teacher moves to a new address, or
  changes her name, the teacher's "record" must be
  changed each place it is stored)
• data inconsistency (different addresses for the
  same teacher in different files)

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• Some Problems with Traditional File Processing
  Systems

• Redundancy (duplication of data)
• wasteful of space (storage)
• update inefficiencies
• (when a teacher moves to a new address, or
  changes her name, the teacher's "record" must be
  changed each place it is stored)
• data inconsistency (different addresses for the
  same teacher in different files)

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LIMITATIONS OF FILE-BASED

• SEPARATION AND ISOLATION
• Payroll Office files has the teachers' names and
  id's and departments
• Principal's Office Files has teachers names ,
  the current salary scale and date this salary
  scale became effective
• Asst. Principal's Office files has seminar topics
  for each teacher
• PROGRAM DATA DEPENDENCE
• The Payroll Department has written some lengthy
  Pascal programs to access their files and perform
  queries and reports.
• The Personnel Department has written some C
  programs to access their files and perform
  queries and reports.

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Database Approach

• Build a SINGLE pool of interrelated files, rather
  than SEPARATE collection of files.
• (This is an INFORMAL description of a database).

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DATABASE

• A COLLECTION OF SELF-DESCRIBING AND INTEGRATED
  ,ORGANISED DATA
• (Kroenke's Definition of a Database)

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DATABASE MANAGEMENT SYSTEM (DBMS)

• A collection of Programs that enables you to
  Store, modify, and extract (access) information
  from a database.
• Provides the interface between the user and the
  data in the database
• Allocates storage to data and maintains indices
  so that any required data can be retrieved.
• Protects data against corruption
• Provides recovery and restart facilities after a
  hardware or software failure.

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Database System

• The DBMS software together with the data itself.
  Sometimes, the applications are also included.

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Database vs. File Systems
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DATABASE MANAGEMENT SYSTEM (DBMS)

• The following are examples of Database
  Applications
• Banking all transactions
• Airlines reservations, schedules
• Universities registration, grades
• Sales customers, products, purchases
• Manufacturing production, inventory, orders,
  supply chain
• Human resources employee records, salaries, tax
  deductions

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DATABASE MANAGEMENT SYSTEM (DBMS)

• Different DBMS Software
• ORACLE
• ACCESS
• SQL SERVER
• IBM DB2
• Sybase
• SAP DB
• PostgreSQL
• MySQL
• MS SQL Server, ...

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Advantages of Database Approach

• Controlling redundancy in data storage and in
  development and maintenance efforts.
• Sharing of data among multiple users.
• Restricting unauthorized access to data.
• Greater consistency of data
• Enforcing integrity constraints on the database.
  
• Providing backup and recovery services.
• Availability of up-to-date information.

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Database System Environment
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Data Models

• Data Model is a set of concepts that can be used
  to describe the structure of a database
• data types, relationships, and constraints
• Data Model Examples
• Relational - describes database structure as
  tables
• Network - describes database structure as a
  network
• Object Oriented - describes database structure as
  objects

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HISTORY OF DATABASE SYSTEMS

• FIRST GENERATION
• _ HIERARCHICAL MODEL
• INFORMATION MANAGEMENT SYSTEM (IMS)
• NETWORK MODEL
• CONFERENCE ON DATA SYSTEM LANGUAGES (CODASYL)
• DATA BASE TASK GROUP (DBTG)
• SECOND GENERATION
• RELATIONAL MODEL
• E. F. CODD
• DB2, ORACLE
• THIRD GENERATION
• EXTENDED RELATIONAL DATA MODEL OR
  OBJECT-RELATIONAL DATA MODEL
• OBJECTED-ORIENTED DATA MODEL

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Schema Architecture

• Database Schema The description of a database.
  It Includes descriptions of the database
  structure and the constraints that should hold on
  the database.

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The three-schema architecture.
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The three-schema architecture.

• External schema describes part of a database that
  a particular user or users are interested in.
• Using the relational model, these are views
• Conceptual schema describes the structure of he
  whole database for a community of users.
• Using the relational model, these are tables
• Internal schema describes the physical storage
  structure of the database.
• These are not tables, this is the data as stored
  by the DBMS.

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ROLES IN DATABASE ENVIRONMENT (USERS)

• DATA ADMINISTRATOR
• Implements the database
• APPLICATION PROGRAMMER
• Interact with the database through high level
  programming
• END-USER
• Interacts and uses the database

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Data Dictionary
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Database Languages

• Data Definition Language (DDL)
• Used to define the conceptual and internal
  schemas
• Data Manipulation Language (DML)
• Used to describe operations on the instances of a
  database
• Procedural DML (how) vs. declarative DML (what)
• e.g., Relational Algebra e.g., SQL
• Note, SQL includes a DML and a DDL in one!

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Database Languages

• DCL Data Control Language. Grant, Revoke
  commands (oracle)
• TCL Transaction control Language Commit,
  Rollback, savepoint commands (oracle)

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• Classification of DBMS based on the data model
  used
• Relational DBMS
• Network DBMS
• Hierarchical DBMS
• Object-oriented DBMS
• Object-relational DBMS

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• Classification of DBMS based on the number of
  users
• Single-user (typically used with micro-
  computers)
• Multi-user (most DBMSs).
• Classification of DBMS based on the number of
  sites
• Centralized (uses a single computer with one
  database)
• Distributed (uses multiple computers, multiple
  databases)