RDBMS UNIT 1 Notes

MODEL QUESTION AND ANSWERS UNITWISE AND MARKWISE
UNIT –1
(2 & 4 MARKS QUESTIONS)
1) Define the following terms: (Definition of each bit:1 Mark)
i) Data ii) Database iii) DBMS iv) RDBMS
Ans:

i) Data: The input or details entered by the user to perform operation on it is known
as data.
OR
Defined as facts, figures or numbers
ii) Database: It is collection of interrelated data which is organized in such a way
that user can access, manage and update easily.
OR
Defined as collection of tables.
iii) DBMS: Collection of interrelated data and set of the programs to operate on it.
OR
DBMS is a software that allows users to create and maintain
(store, modify and extract data from database) a database.
iv) RDBMS: A relational database management system is a database management
system used to manage relational databases.
A relational database is one where tables of data can have relationships
based on primary and foreign keys.
2) Explain two disadvantages of file processing system.(Any2 Disadvantages–2Meach)
Ans:
Disadvantages of file processing system
1. Data redundancy and inconsistency :
Since the files and application programs are created by different programmers
over a long period, the various files are likely to have different formats and
the programs may be written in several programming languages.
So , the same information may be duplicated in several places (files).
That repetition of information is known as redundancy.
This redundancy leads to higher storage and access cost.
In addition, it may lead to data inconsistency, that is different copies of the
same data may have different values.
2. Difficulty in accessing data :
The conventional file processing system do not allow to access data in a
convenient and efficient way.
As the data was scattered in different files and whenever need arises
different application programs were written by different programmers in different formats.
3. Data isolation
As the data scattered in various files and files may be in different formats,
writing new application programs to retrieve the data is very difficult.
4. Integrity problems
The data values stored in the database must satisfy certain types of
consistency constraints.
When new constraints are added, it is difficult to change the programs to
enforce them.
5. Atomicity problems
A computer system, like any other mechanical or electrical device, is subject to failure.
If any failure occurs in the system the transaction which are executing should
fully get executed or should not, so that database remains in consistent state.
6. Concurrent-access anomalies
To improve the performance of the system, multiple transactions must get executed concurrently.
Multiple transactions may be updating the same data concurrently.
In such case the data may result in inconsistent state
7. Security problems
Only authorized person should be able to modify the data.
Security should be maintained at different levels which were not possible in file processing system.
3) What is data redundancy? (Definition of data redundancy-2 Marks)
Ans:
Data redundancy means storing same data multiple times at different locations.
4) Explain Data Redundancy and Integrity.(Each Explanation – 2 Marks each)
Ans:
Data redundancy :Data redundancy is the unnecessary repetition of data.
Since different programmers create the files and application programs over a long
period ,the various files are likely to have different structures and programs may be
written in several programming languages.
The same piece of information or program may be duplicated in several places.
e.g. accounting department and registration department both keep student name,
number and address.
Data Redundancy
 Increases the size of the database unnecessarily
 Causes data inconsistency.
 Increases the access cost and decreases efficiency of database.
 May cause data corruption.
Such data redundancy in DBMS can be prevented by database normalization.
Data integrity:
 Data integrity refers to maintaining and assuring the accuracy and
consistency of data over its entire life-cycle.
 Data integrity is usually imposed during the database design phase
through the use of standard procedures and rules.
 Data integrity can be maintained through the use of various error checking methods and validation procedures.
e.g. The balance of certain type of bank account may never fall below a prescribed
amount(Rs.5000).
We can handle this through program code and declaring integrity constraint
along with definition.
5) State and explain four advantages of DBMS over file processing system.
(Any four Advantage – 1 Mark each)
Ans:
1. Reduction in Redundancy: Duplication of records is reduced.
2. Avoiding Inconsistency: As the redundancy is reduced inconsistency is avoided.
3. Maintaining Integrity: Accuracy is maintained.
4. Sharing of data: Sharing of data is possible.
5. Enforcement of Security: Security can be enforced.
6. Transaction support
6) Explain any four functions of DBMS. (Consider any four function – 1 Mark each
(Any other functions of DBMS is considered))
Ans:
Database Communication Interfaces:
The end-user’s requests for database access are transmitted to DBMS in the form of communication messages.
Authorization / Security Management:
The DBMS protects the database against unauthorized access, either
international or accidental.
It furnishes mechanism to ensure that only authorized users an access the database.
Backup and Recovery Management:
The DBMS provides mechanisms for backing up data periodically and recovering from different types of failures.
This prevents the loss of data.
Concurrency Control Service:
Since DBMSs support sharing of data among multiple users, they must
provide a mechanism for managing concurrent access to the database.
DBMS ensure that the database kept in consistent state and that integrity of the data is preserved.
Transaction Management:
A transaction is a series of database operations, carried out by a single user or application program, which accesses or changes the contents of the database. Therefore, a DBMS must provide a mechanism to ensure either that all the updates corresponding to a given transaction are made or that none of them is made.
Database Access and Application Programming Interfaces:
All DBMS provide interface to enable applications to use DBMS services.
They provide data access via Structured Query Language (SQL).
The DBMS query language contains two components:
(a) a Data Definition Language (DDL) and
(b) a Data Manipulation Language (DML).
Data integrity and consistency:
To provide data integrity and data consistency, the DBMS uses sophisticated
algorithms to ensure that multiple user can access the database concurrently
without compromising the integrity of the database.
7) Define DBMS. List any two applications of DBMS.
(Definition- 1 Mark, Any 2 Application- 1/2 Mark each, Any relevant applications can
be considered)
OR
7) List any four application of DBMS.
(Each Application: 1/2 Marks, Any relevant applications can be considered)
Ans:
DBMS:
A database-management system is a collection of interrelated data and a set
of programs to access those data.
Applications of DBMS:
1. Banking
2. Airlines and railways
3. Sales
4. Telecommunications
5. Universities.
6. Manufacturing
7. E-commerce
8. Credit card transactions.
8) Differentiate between DBMS and RDBMS.
(Any 4 valid differences – 1 Mark each)

DBMS RDBMS
1.Database Management System 1. Relational Database Management System
2. It is mainly used for storage of data and efficient retrieval. 2. It is that environment where data is represented in the form of relations, with enforced relationships between the tables.
3. Mainly used for single user system 3. Generally used in multiuser environment.
4. Not all Codd rules are satisfied. 4. All 12 Codd rules are satisfied.
5. Suitable for low volume of data 5. Suitable for large volume of data
6. Security is less. 6. More security measures provided
7. Example : Forxpro, dbaseIII plus 7. Example : Oracle, SQL Server
8. Old version of software to handle the databases. 8.Latest version of software for handling databases.
9. Can relate one table to another table. 9.RDBMS can relate one database to another database.
10.Data storage capacity is less as compare to RDBMS. 10.Data storage capacity is very high.
11. Not easy to maintain data integrity. 11.Data integrity is one of the most important features of RDBMS. It can be maintained easily in RDBMS.

9) What is data abstraction? What are the levels of abstraction?
( Data abstraction – 1 Mark , Three levels – 3Marks)
OR
9) Describe data abstraction with neat diagram.
(Diagram- 1 Mark, Description of each level-1 Mark)
Ans:

Untitled

 

Explanation:
1) Physical Level:
 It is lowest level of abstraction.
 This level defines lowest complicated data structure of database system.
 This level hidden from user.
 It defines how the data are stored.
2) Logical Level:
 The level next to physical level is called logical level.
 This level defines what data stored in the database and what the
relationships among these data are.
 Fully decides the structure of the entire database.
3) View Level:
 This level is used to show the part of database to user.
 There is more complexity in physical as well as logical level so user
should not interact with complicated database.
 So different view of database can be created for user to interact with
database easily.
10) What is data abstraction, instances and schema?
(Data Abstraction – 2 Marks, Instance – 1 Mark, Schema – 1 Mark)
Ans:
Data Abstraction: Data abstraction can be defined as the process of hiding the
complexity of data and representing the data which needs to be shown to users.
There are three levels of data abstraction:
1. Physical level
2. Conceptual / logical level
3. View level
Schema:
The overall design of the database is known as schema.
The database schemas are partitioned at different level of abstractions.
Instance:
The collection of information stored in the databases at a particular moment
is called as an instance.
11) Describe data independence with its type.
(Definition of Data independence- 1Mark, Types of data independence – 1/2 Mark each)
Ans:
Data independence:
The ability to modify a schema definition in one level without affecting a
schema definition in next higher level is called data independence.
There are two types of data independence.
1. Physical data independence
Physical data independence is the ability to change internal level without
having change in conceptual or external level.
2. Logical data independence
Logical data independence is the ability to change conceptual level without
having change in external level or application program.
12) Draw diagram for overall architecture of DBMS.
(Correct diagram – 4 Marks)
Ans

Untitled

 

13) List and explain types of DBMS users. (List – 2 Marks, Any two types -1 Mark
each) Ans:
List of DBMS user.
a) Naive users b) Application programmers
c) Sophisticated users d) Specialized users
Explanation:
a) Naive User:
 Naive users are unsophisticated users.
 They are interact with the system through the application program.
 They give data as input through application program or get output data
which is generated by application program.
 Example: Bank cashier.
b) Application programmers:
 Application programmers are the users who write the program.
 These programmers use programming tools to develop the program.
 RAD technology is used to write the program.
c) Sophisticated users:
 Sophisticated users interact with the system by making the requests in
the form of query language.
 These queries are then submitted to the query processor.
 Query processor converts the DML statements into lower level
interactions which are understandable by storage manager.
 Some sophisticated users can be analyst.
d) Specialized users:
 These users are not traditional.
 They write some special application programs which are not regular
applications.
 Example: such types of applications are CAD, knowledge based and
expert system.
14) List four function of database administrator.
(List any four function – 1 Mark each)
OR
14) List and explain any four functions of database administrator.
(List & Explanation: 1Mark each (any 4))
Ans:
List of functions of DBA:
1. Schema Definition
2. Storage structure and access method definition
3. Schema and physical organization modification
4. Granting authorization for data access
5. Routine Maintenance
Function of database administrator
1. Schema Definition:
The DBA creates database schema by executing DDL statements.
2. Storage structure and access method:
The storage of the data structure and how to access data
from it is handled by DBA.
3. Granting of authorization for data access:
The DBA will grant and restrict access to the user
4. Regular Maintenance of Database:
The DBA performs some of the routine maintenance activities like
periodic backups, ensuring enough disk space is available.
5. Schema and Physical organization modification:
DBA writes a set of definitions to modify the database schema or
description of physical storage organization.
6. Integrity-constraint specification:
Integrity constraints are written by DBA and they are stored in a
special file, which is accessed by database manager, while updating the
data.
7. Back-up and Recovery:
DBA also takes backup of the data on a backup storage device so that
if data then lost then it can be again recovered and compiled.
DBA also recovers the damaged data.
15)What is client server architecture? Draw Diagram.
[Explanation 2 Marks, Diagram 2 Marks]
Ans:
 Computer networking allows some task to be executed on a server system and some
tasks on client system.
 This leads to development of client server architecture.
 The clients are the machines which requests for the service to the server.
 Server is the machine which serves to the clients.
 There are different types of client/server architecture such as two tier, three tier
architecture.
 In two tier architecture, client systems directly approach database servers whereas in
three tier architecture, there exists a middle layer which acts as application server to
receive and send requests from client machine to database server and vice versa.

Untitled

 

16) Explain three tier architecture with diagram. (Explanation – 2M, Diagram – 2 M)
Ans:
 In three tier architecture the communication taken place from client to
application server and then application server to database system to access the data.
 The application server or web server is sometimes called middle layer or intermediate layer.
 The middle layer which processes applications and database server processes the queries.
 This type of communication system is used in the large applications or the world web applications.
 On WWW all clients requests for data and server serves it.
 There are multiple servers used like fax server, proxy server, mail server etc

Untitled

 

17) List first four codd rules.(For each rule – ½ Mark)
Ans: list of codd rules:
Rule 1 : The information rule
Rule 2 : Guaranteed Access Rule
Rule 3: Systematic treatment of null values
Rule 4 : Dynamic on-line catalog based on the relational model
Rule 5 : Powerful language
Rule 6 : view updation rule
Rule 7 : Relational level operation
Rule 8 : Physical level independence
Rule 9 : Logical level independence
Rule 10 : Integrity independence
Rule 11 : Distribution independence
Rule 12 : No subversion rule

Explanation:
Rule 1 : The information rule
According to E.F. codd’s first rule, the whole data has to be presented to the user should be in the form of table.
Rule 2 : Guaranteed Access Rule
According to second rule stated by E.F. codd, whole data should be
available or accessible to the user without any ambiguity.
The ambiguity can be avoided only through the perfect combination
of the table name, primary key, and column name.
Rule 3: Systematic treatment of null values
Third law states that the null values i.e. absence of the values in the
table should be treated properly.
The table should allow a field to remain empty.
This is not applicable to primary keys.
Key columns cannot have null values.
Rule 4 : Dynamic on-line catalog based on the relational model
Fourth rule specifies need of dynamic on-line catalog based on the
relational model.
There are certain system tables that stores the database definition
should be present.
The data accessing tools should be used to access the database structure information.
18) Explain data mining. List four features of data mining.
(Explanation – 2 Marks, for each relevant correct features – ½ Mark)
Ans:
 Data mining is the exploration and analysis of large quantities of data in
order to discover valid, novel, potentially useful and ultimately
understandable patterns in data.
 It is known as “Knowledge Discovery in Databases”.
 When the data is stored in large quantities in data warehouse, it is necessary
to dig the data from the ware house that is useful and required for further use.
 For data mining, different software tools are used to analyze, filter and
transfer the data from the data warehouses.
Feature of data mining:
1) Prediction
2) Identification
3) Classification
4) Optimization

19) What is data mining and data ware housing?
(Each Explanation – 2 Marks each)
Ans:
Data Mining :-
 Data mining is the exploration and analysis of large quantities of data in
order to discover valid, novel, potentially useful and ultimately
understandable patterns in data.
 It is known as “Knowledge Discovery in Databases”.
 When the data is stored in large quantities in data warehouse, it is necessary
to dig the data from the ware house that is useful and required for further use.
 For data mining, different software tools are used to analyze, filter and
transfer the data from the data warehouses.
Data Warehousing:-
 A data warehouse is a repository of information gathered from multiple
sources, stored under a unified schema, at a single site.
 Once gathered, data are stored for long time, permitting access to historical
data.
 Data warehouses provide the user a single consolidated interface to data,
making decision-support queries easier to write.
 Moreover, by accessing information for decision support from a data
warehouse, the decision makers ensures that online transaction-processing
systems are not affected by decision support workload.

Leave a Reply

Your email address will not be published. Required fields are marked *