No centralized control of data.
Multiple file formats, duplication of information in different
Each app. has its own private files & users has little chance
to share data outside their own app.
Each different data access request (a query) performed by a
Creating the system requires a lot of effort
For each new application, programmers have to design
their own file formats & descriptions from scratch.
Excessive Program Maintenance: 80% of information
Need to write a new program to carry out each new task.
Data Redundancy (Duplication of data).
A database is an organised collection of related data
ƒ Representing/capturing the information about
a real-world , enterprise or part of an enterprise.
• ƒ Collected and maintained to serve specific data
management needs of the enterprise.
• It can be of varying size and complexity .
By data, we mean known facts that can be recorded.
For example: University Database
• Data about students, faculty, courses,
research laboratories, course registration/
• Purpose: To keep an accurate track of the
academic activities of the university.
It is a database of images that
scientists use for international
collaboration, research and
Manager: is a
organizer for PC
users who want
to keep track of
anything in their
Advantages of database over file system
Efficiency: highly efficient as data is stored in one central location.
Minimal Data Redundancy: reduce file duplication.
Data Consistency: less redundancy leads to consistency.
Data Integration: Since related data is stored in one single database, enforcing
data integrity is much easier..
Data Sharing: Related data can be shared across programs since the data is
stored in a centralized manner.
Better Controls: Better controls can be achieved due to the
centralized nature of the system
Application Development Ease: no need to write different programmes for
Reduced Maintenance: Maintenance is less and easy, again, due to the
centralized nature of the system.
Providing backup and recovery services.
0’s and 1’s
Combination of 0’s and 1’s
Combination of characters. Name, roll
no, class, rank
Record of MBA 1st sem.
Record of each student of MBA 1st
Record of MBA 1st and 4th sem.
Database management system (dbms):Software to manipulate database.
Metadata : Data that describe the properties or characteristics of end-user
Database administrator : Persons who are responsible for the overall
management of data resources
Database system: Comprised of database, DBMS, and application programs
System developers: Programmers who design new application
End users : Who request or receive information from it.
Computer-aided software engineering (case) tools: CASE tools are
automated tools used to design databases and application programs.
Database management system (DBMS)
• A database management system (DBMS) is a general purpose
software system that:
• Defines, creates, and maintains a database.
• Allow access to data in database.
Levels of database
The Internal level : It is the physical level which shows how the data is stored,
how bytes are transferred to and from storage devices. It interacts directly with
The Conceptual level: It is the representation of the entire information content
of the database. Main functions of DBMS are also defined on this level.
The External Level : Represents the collection of views available to different
end-users. It changes data coming from conceptual level to a format and view that
is familiar to users.
TYPES OF ATTRIBUTES
• DOESN’T CONTAIN MEANINGFUL SMALLER
• IF IT CONTAINS ONE OR MORE COMPONENTSADDRESS- HOUSE NO. STREET NO. PIN CODE
• HAVING SINGLE VALUE
• AGE, NAME
• MORE THAN ONE VALUE
• PHONE NUMBER, ID’s
• THAT CAN BE DERIVED FROM OTHER
• THAT CAN BE FOUND WITH HELP OF OTHER
ATTRIBUTES - DATE OF BIRTH
• THAT HAVE VALUE ONLY FOR PARTICULAR
Types of database models
Hierarchical database model
Logically represented by an upside down tree
Each entity have one parent but can have several parents.
At top of hierarchy there is only one entity called root.
Network data model
Each record can have multiple parents.
Each entity can be accessed through several paths.
Relational database model
RDBMS: the relational database management system
Relation: a relation is a 2D table has the following
Relational database model
All data is maintained in the form of tables consisting of
rows and columns.
Operators are provided.
This, in fact, is a major reason for the relational model to
become more programmer friendly and much more
dominant and popular.
Oracle, Sybase, DB2, Ingres, Informix, MS-SQL Server are
few of the popular Relational DBMSs.
A row or a record in a relation.
A field or a column in a relation.
Cardinality of a relation
The number of tuples in a relation.
Degree of a relation
The number of attributes in a relation.
An attribute or a combination of attributes in one
relation R1 connecting it to R2
of a relation
An attribute or a combination of attributes that
uniquely defines each tuple in a relation.
Handles more relationship types
Data access flexibility
Promotes database integrity
Conformance to standards
Lack of structural independence
DATA DEFINITION LANGUAGE (DDL)
Collection of instructions and commands used to define and describe data and data
Detailed description of all data used in the database.
Provide a standard definition of terms and data elements
DATA MANIPULATION LANGUAGE (DML)
Allows users to access, modify, and make queries about data contained in the database
A view of just a portion of a database records and/or fields as desired by user.