Database

1
Database

• A database is a logically coherent collection of
  data with some inherent meaning e.g. address book
• A database is designed, built, and populated with
  data for a specific purpose

2
Database

• A database may be generated and maintained
  manually, for example, a library card
  catalog.
• A computerized database is usually maintained by
  a set of programs.

3
Data Hierarchy

• File (Collection of related records)
• Record (data elements that relate to a particular
  object or activity)
• Data element (smallest unit of data)

4
Traditional Approach

• Programming with files or file-processing
• Files linked to a specific application
• Structure of data files is embedded in the
  application programs

5
File Processing - Disadvantages

• File structure changes usually result in program
  changes
• Data redundancy or duplication
• Wasted space
• Naming problems
• Inconsistency because of lack of synchronization
  in updating the duplicated data

6
File Processing -Disadvantages

• Diffused data ownership
• programmers own data accessed by their programs
• Result - inconsistent, inaccurate, and unreliable
  information

7
Database Approach

• A single repository of data which is accessed by
  various users
• Database system contains the database and a
  complete description of the database called
  meta-data

8
Database Approach - Advantages

• Program - data independence
• Ability to change data structure without making
  changes to the programs
• User is not constrained by the physical
  organization of data

9
Database Management System (DBMS)

• DBMS is a collection of programs that enables
  users to create and maintain a database
• DBMS is a general-purpose software that
  facilitates the process of defining constructing
  and manipulating databases for various
  applications

10
DBMS (Contd.)

• DBMS functions
• Defining a database (data types, structures, and
  constraints)
• Constructing the database (storing the data)
• Manipulating the database (querying, updating and
  report generation)
• DBMS software database database system

11
A Simplified Database SystemEnvironment
Users/Programmers
DATABASE SYSTEM
Application Programs/Queries
DBMS Software
Software to Process Queries/Programs
Software to Access Stored Data
Stored Database Definition (Meta-Data)
Stored Database
12
DBMS (Contd.)

• Data hierarchy in a Database Approach
• Database (collection of interrelated files)
• File
• Record
• Data element
• Means to integrate the contents of files that
  have logical relationship

13
Database Structures

• Logical integration of files through explicit
  relationships - for example, link fields in a
  hierarchical structure
• Implicit relationships - relationships that can
  be implied from existing record data as in a
  relational structure

14
Database Approach - Disadvantages

• Need for DBMS software which could be expensive
• Larger hardware configuration may be needed
• Dedicated staff

15
Database Staff

• Database Administrator (DBA)
• authorizes access to the database
• co-ordinates and monitors database use
• acquires software and hardware resources
• accountable for security and response time
  problems

16
Database Staff (Contd.)

• Analysts/Database designers
• get user requirements
• identify data to be stored
• choose appropriate structures
• develop a view of the database that meets user
  requirements
• Programmers