This document discusses databases and database management systems. It defines a database as a collection of organized data that can be easily accessed, managed, and updated. A database management system (DBMS) is system software that allows users to create, retrieve, update, and manage data in a database. A DBMS serves as an interface between the database and users or applications, ensuring consistent organization and accessibility of data. The document also describes three levels of data abstraction - physical, conceptual, and external - and three common database models: hierarchical, network, and relational.

2. Database
Collection of Data or Information referred to database.

3. A database is a collection of
information that Is organized so that
it can be easily accessed, managed
and updated.
Data is organized into rows,
columns and tables, and it is indexed
to make it easier to find relevant
information.

4. Database management system
[BDMS]
A database management system
[BDMS] is system software for
creating and managing database.
The [BDMS] provide users
and programmers with a systematic
way to create, retrieve, update and
manage data.

5. A BDMS makes it possible for end users to
create, read, update and delete data in a
database. The BDMS essentially serves as
an interface between the database and end
users or application programs, ensuring
that data is consistently organized and
remains easily accessible.

7. Various levels of database implementation
 Physical level.
It shows that how the data are actually stored on the storage
medium.
It is related to the database programmers. And the lowest level of
database abstraction.
Conceptual level.
It shows that what data is actually stored in database.
It is related to the database manager. And intermediate level of database
abstraction.
External level.
It shows the way in which the data are viewed by individual user.
It is
the closest level to the users.

8. Three levels of data
abstraction

9. Database models
Hierarchical database model.
The type of model, data is organized into a tree like structure. There is a
hierarchy of parent and child segments. The structure implies that a record
can have repeating information, usually in a child data segment.
.network database
model. It is
similar to a hierarcihal database model concept except that each child can
have more than parent record. A child record is referred to as a ‘member’
and a parent record is an ‘owner’ the advantage of the network database is
its ability establish relationship between different branches of data records
and thus offer increased access capability for the manager .

10. Relational database model. A
relation is a table with columns and rows. the relational model uses a
collection of tables/relations to represent both data and the relationship
among those data. Each table has multiple columns and each column has
a unique name. information about particular entity is represented in
rows(also called tuples) and columns.

14. Prepared by mansoor badshah