Database Management System

1. DBMS
UNIT I

2. Data
● Data is information that has been translated into a form that is efficient for movement
or processing.
● Data can be facts related to any object
Eg- your name, age, etc.

3. Database
● A database is a collection of information that is organized so that it can be easily be
accessed, managed and updated.

4. Database Management System
● DBMS provides an interface to perform various operation like database creation,storing
data in it , updating data, creating a table in the database and lot more.
● It Provides protection and security to the database. In the case of multiple user ,it also
maintains data consistency( Duplication of data)
● Contain a query language to retrieve information easily
● Eg Oracle, SQL Server , IBMDB2, Amazon Simple DB(Cloud Based)
● My Sql (freely Available)

5. Disadvantages of File Processing System
● Data Redundancy problem.
○ Repetition of information
○ Space utilization is more access time increases
● Atomicity Problem
○ Transaction should be fully completed
● Data isolation problem
○ Each transaction must be executed without knowing what is happening with other transaction
● Data Integrity problem
○ It refers to the overall accuracy and completeness of data in a database.
● Data inconsistency problem
○ Same data exist in different format in multiple table
○ Eg address change in one table should be reflected in other table also

6. Disadvantages of File Processing System

7. Advantages of DBMS
● Controls database redundancy: It can control data redundancy because it stores all the data in one single
database file and that recorded data is placed in the database.
● Data sharing: In DBMS, the authorized users of an organization can share the data among multiple users.
● Easily Maintenance: It can be easily maintainable due to the centralized nature of the database system.
● Reduce time: It reduces development time and maintenance need.
● Backup: It provides backup and recovery subsystems which create automatic backup of data from
hardware and software failures and restores the data if required.
● multiple user interface: It provides different types of user interfaces like graphical user interfaces,
application program interfaces

8. Disadvantages of DBMS
● Cost of Hardware and Software: It requires a high speed of data processor and large memory size
to run DBMS software.
● Size: It occupies a large space of disks and large memory to run them efficiently.
● Complexity: Database system creates additional complexity and requirements.
● Higher impact of failure: Failure is highly impacted the database because in most of the
organization, all the data stored in a single database and if the database is damaged due to electric
failure or database corruption then the data may be lost forever.

9. DBMS Architecture
● The DBMS design depends upon its architecture. The basic client/server architecture is
used to deal with a large number of PCs, web servers, database servers and other
components that are connected with networks.
● The client/server architecture consists of many PCs and a workstation which are
connected via the network.
● DBMS architecture depends upon how users are connected to the database to get their
request done.

10. DBMS Architecture

11. DBMS Architecture
1-Tier Architecture
● In this architecture, the database is directly available to the user. It means the user can directly
sit on the DBMS and uses it.
● Any changes done here will directly be done on the database itself. It doesn't provide a handy
tool for end users.
● The 1-Tier architecture is used for development of the local application, where programmers
can directly communicate with the database for the quick response.

12. DBMS Architecture
2-Tier Architecture
● The 2-Tier architecture is same as basic client-server. In the two-tier architecture, applications
on the client end can directly communicate with the database at the server side. For this
interaction, API's like: ODBC, JDBC are used.
● The user interfaces and application programs are run on the client-side.
● The server side is responsible to provide the functionalities like: query processing and
transaction management.
● To communicate with the DBMS, client-side application establishes a connection with the
server side.

13. DBMS Architecture
2-Tier Architecture

14. DBMS Architecture
3-Tier Architecture

15. DBMS Architecture
3-Tier Architecture
The 3-Tier architecture contains another layer between the client and server. In this architecture, client
can't directly communicate with the server.
● The application on the client-end interacts with an application server which further communicates
with the database system.
● End user has no idea about the existence of the database beyond the application server. The database
also has no idea about any other user beyond the application.
● The 3-Tier architecture is used in case of large web application.

16. Three level schema Architecture

17. DBMS Architecture
1. Internal Level
● The internal level has an internal schema which describes the physical storage structure
of the database.
● The internal schema is also known as a physical schema.
● It uses the physical data model. It is used to define that how the data will be stored in a
block.
● The physical level is used to describe complex low-level data structures in detail.

18. DBMS Architecture
2. Conceptual Level
● The conceptual schema describes the design of a database at the conceptual level. Conceptual
level is also known as logical level.
● The conceptual schema describes the structure of the whole database.
● The conceptual level describes what data are to be stored in the database and also describes
what relationship exists among those data.
● In the conceptual level, internal details such as an implementation of the data structure are
hidden.
● Programmers and database administrators work at this level.

19. DBMS Architecture
3. External Level
● At the external level, a database contains several schemas that sometimes called
as subschema. The subschema is used to describe the different view of the
database.
● An external schema is also known as view schema.
● Each view schema describes the database part that a particular user group is
interested and hides the remaining database from that user group.
● The view schema describes the end user interaction with database systems.

20. DBMS Abstraction Example:- IRCTC
How data is actually stored in the database
What data is stored in the database
Not aware of storing the user just interact with database.

21. DBMS Model
A Database model defines the logical design and structure of a database and defines
how data will be stored, accessed and updated in a database management system.
While the Relational Model is the most widely used database model, there are other
models too:
● Hierarchical Model
● Network Model
● Entity-relationship Model
● Relational Model

22. Hierarchical Model
● This database model organises data into a tree-like-structure, with a single root, to which all
the other data is linked. The hierarchy starts from the Root data, and expands like a tree,
adding child nodes to the parent nodes.
● In this model, a child node will only have a single parent node.
● This model efficiently describes many real-world relationships like index of a book, recipes
etc.
● In hierarchical model, data is organised into tree-like structure with one-to-many relationship
between two different types of data, for example, one department can have many courses,
many professors and of-course many students.

23. Hierarchical Model

24. Network Model
● This is an extension of the Hierarchical model. In this model data is organised more like a
graph, and are allowed to have more than one parent node.
● In this database model data is more related as more relationships are established in this
database model. Also, as the data is more related, hence accessing the data is also easier and
fast. This database model was used to map many-to-many data relationships.
● This was the most widely used database model, before Relational Model was introduced.

25. Network Model

26. Entity-relationship Model
● In this database model, relationships are created by dividing object of interest into entity and its
characteristics into attributes.
● Different entities are related using relationships.
● E-R Models are defined to represent the relationships into pictorial form to make it easier for
different stakeholders to understand.
● This model is good to design a database, which can then be turned into tables in relational
model(explained below).
● Let's take an example, If we have to design a School Database, then Student will be an entity with
attributes name, age, address etc. As Address is generally complex, it can be another entity with
attributes street name, pincode, city etc, and there will be a relationship between them.

27. Entity-relationship Model

28. Relational Model
● In this model, data is organised in two-dimensional tables and the relationship is maintained
by storing a common field.
● This model was introduced by E.F Codd in 1970, and since then it has been the most widely
used database model, infact, we can say the only database model used around the world.
● The basic structure of data in the relational model is tables. All the information related to a
particular type is stored in rows of that table.
● Hence, tables are also known as relations in relational model.

29. Relational Model

30. Component of ER Model
Rectangle: Represents Entity sets.
Ellipses: Attributes
Diamonds: Relationship Set
Lines: They link attributes to Entity Sets and Entity sets to Relationship Set
Double Ellipses: Multivalued Attributes
Dashed Ellipses: Derived Attributes
Double Rectangles: Weak Entity Sets
Double Lines: Total participation of an entity in a relationship set