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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
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.
Data Hierarchy
File (Collection of related records)
Record (data elements that relate to a
particular object or activity)
Data element (smallest unit of data)
Traditional Approach
Programming with files or file-processing
Files linked to a specific application
Structure of data files is embedded in the
application programs
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
File Processing Disadvantages
Diffused data ownership
programmers “own” data accessed by their
programs
Result - inconsistent, inaccurate, and
unreliable information
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
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
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
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
A Simplified Database System
Environment
Users/Programmers
DATABASE Application Programs/Queries
SYSTEM
DBMS
Software
Software to Process
Queries/Programs
Software to Access
Stored Data
Stored Database
Definition
(Meta-Data)
Stored Database
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
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
Database Approach “Disadvantages”
Need for DBMS software which could be
expensive
Larger hardware configuration may be
needed
Dedicated staff
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
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