Database Concepts: Book Back Questions and Answers

Computer Science : Database concepts and MySql : Database Concepts

Evaluation

Part – A

Choose the best answer (1 Marks)

1.  What is the acronym of DBMS? 

a) DataBase Management Symbol

b) Database Managing System

c) DataBase Management System

d) DataBasic Management System

2  A table is known as

a) tuple

b) attribute

c) relation

d)entity

3  Which database model represents parent-child relationship?

a) Relational

b) Network

c) Hierarchical

d) Object

4  Relational database model was first proposed by

a) E F Codd

b) E E Codd

c) E F Cadd

d) E F Codder

5  What type of relationship does hierarchical model represents?

a) one-to-one

b) one-to-many

c) many-to-one

d) many-to-many

6.  Who is called Father of Relational Database from the following?

a) Chris Date

b)Hugh Darween

c) Edgar Frank Codd

d) Edgar Frank Cadd

7.  Which of the following is an RDBMS?

a) Dbase

b) Foxpro

c) Microsoft Access

d) SQLite   

8  What symbol is used for SELECT statement?

a) σ

b) Π

c) X

d) Ω

9  A tuple is also known as

a) table

b) row

c) attribute

d) field

10. Who developed ER model?

a) Chen

b) EF Codd

c) Chend

d) Chand    

Part – B

Answer the following questions (2 Marks)

1. Mention few examples of a database.

Ans. (i) Foxpro

(ii) DBase

(iii) ADABAS

(iv) Microsoft Excel

(v) Microsoft Square

(vi) Oracle RDBMS

(vii) MySQL

2. List some examples of RDBMS.

Ans. (i) IBM DBZ

(ii) Microsoft SQL Server

(iii) Microsoft Jet Database Engine

(iv) MySQL

(v) Oracle

(vi) SQLite

3. What is data consistency?

Ans. Data Consistency means that data values are the same at all instances of a database

4. What is the difference between Hierarchical and Network data model?

Ans. The difference between Hierarchical and Network data model is :

(i) In hierarchical model, a child record has only one parent node,

(ii) In a Network model, a child may have many parent nodes. It represents the data in many-to-many relationships.

(iii) This model is easier and faster to access the data.

5. What is normalization?

Ans. Database normalization is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity.

Part –C

Answer the following questions (3 Marks)

1. What is the difference between Select and Project command?

Ans.

Select

It selects tuples that satisfy the given predicate from a relation

Symbol: σ

Project

It projects column(s) that satisfy a given predicate. Duplicate rows are automatically eliminated as relation is a set

Symbol: π

2. What is the role of DBA?

Ans. Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.

3. Explain Cartesian Product with a suitable example.

Ans. (i) Cross product is a way of combining two relations. The resulting relation contains, both relations being combined.

(ii) A × B means A times B, where the relation A and B have different attributes.

(iii) This type of operation is helpful to merge columns from two relations.

4. Explain Object Model with example.

Ans. Object Model : Object model stores the data in the form of objects, attributes and methods, classes and inheritance. This model handles more complex applications, such as Geographic information System (GIS), scientific experiments, engineering design and manufacturing. It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model.

(i) Circle has the attribute radius.

(ii) Rectangle has the attributes length and breadth.

(iii) Triangle has the attributes base and height.

(iv) The objects Circle, Rectangle and Triangle inherit from the object Shape.

5. Write a note on different types of DBMS users.

Ans. Type of DBMS Users

(i) Database Administrators: Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.

(ii) Application Programmers or Software Developers : This user group is involved in developing and designing the parts of DBMS.

(iii) End User: All modern applications, web or mobile, store user data. Applications are programmed in such a way that they collect user data and store the data on DBMS systems running on their server. End users are the one who store, retrieve, update and delete data.

(iv) Database designers: are responsible for identifying the data to be stored in the database for choosing appropriate structures to represent and store the data. 

Part –D

Answer the following questions (5 Marks)

1. Explain the different types of data model.

Ans.The different types of a Data Model:

Hierarchical Model, Relational Model, Network Database Model, Entity Relationship Model, Object Model.

Hierarchical Model:

(i) Hierarchical model was developed by IBM as Information Management System. In Hierarchical model, data is represented as a simple tree like structure form.

(ii) This model represents a one-to-many relationship i.e., parent-child relationship. One child can have only one parent but one parent can have many children.

(iii) This model is mainly used in IBM Main Frame computers.

Relational Model:

(i) The Relational Database model was first proposed by E.F. Codd in 1970 . Nowadays, it is the most widespread data model used for database applications around the world.

(ii) The basic structure of data in relational model is tables (relations). All the informations related to a particular type is stored in rows of that table.

(iii) Hence tables are also known as relations in a relational model. A relation key is an attribute which uniquely identifies a particular tuple (row in a relation (table)).

Network Model: Network database model is an extended form of hierarchical data model. The difference between hierarchical and Network data model is:

(i) In hierarchical model, a child record has only one parent node,

(ii) In a Network model, a child may have many parent nodes. It represents the data in many-to-many relationships.

(iii) This model is easier and faster to access the data.

(iv) School represents the parent node

(v) Library, Office and Staff room is a child to school (parent node)

(vi) Student is a child to library, office and staff room (one to many relationship)

Entity Relationship Model. (ER model):

(i) In this database model, relationship are created by dividing the object into entity and its characteristics into attributes.

(ii) It was developed by Chen in 1976. This model is useful in developing a conceptual design for the database. It is very simple and easy to design logical view of data. The developer can easily understand the system by looking at ER model constructed.

(iii) Rectangle represents the entities. E.g. Doctor and Patient.

(iv) Ellipse represents the attributes E.g. D-id, D-name, P-id, P-name. Attributes describes the characteristics and each entity  becomes a major part of the data stored in the database. Diamond represents the relationship in ER diagrams

E.g. Doctor diagnosis the Patient

Object Model:

(i) Object model stores the data in the form of objects, attributes and methods, classes and Inheritance.

(ii)This model handles more complex applications, such as Geographic information System (GIS), scientific experiments, engineering design and manufacturing.

(iii) It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

 (iv)  An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model.

■ Circle has the attribute radius.

■ Rectangle has the attributes length and breadth.

■ Triangle has the attributes base and height.

■ The objects Circle, Rectangle and Triangle inherit from the object Shape.

2. Explain the different types of relationship mapping.

Ans. The types of relationships used in a database.

(i) One-to-One Relationship

(ii) One-to-Many Relationship

(iii) Many-to-One Relationship

(iv) Many-to-Many Relationship

(i) One-to-One Relationship: In One-to- One Relationship, one entity is related with only one other entity. One row in a table is linked with only one row in another table and vice versa.

For example : A student can have only one exam number

(ii) One-to-Many Relationship: In One-to- Many relationship, one entity is related to many other entities. One row in a table A is linked to many rows in a table B, but one row in a table B is linked to only one row in table A.

For example: One Department has many staff members.

(iii) Many-to-One Relationship: In Many- to-One Relationship, many entities can be related with only one in the other entity.

 For example: A number of staff members working in one Department. Multiple rows in staff members table is related with only one row in Department table.

(iv) Many-to-Many Relationship: A many- to-many relationship occurs when multiple records in a table are associated with multiple records in another table.

■ Example 1 : Customers and Product

Customers can purchase various products and Products can be purchased by many customers

■ Example 2 : Students and Courses

A student can register for many Courses and a Course may include many students

■ Example 3 : Books and Student.

Many Books in a Library are issued to many students.

3. Differentiate DBMS and RDBMS.

Ans.

4. Explain the different operators in Relational algebra with suitable examples.

Ans. Relational Algebra is divided into various groups

Unary Relational Operations :

■ SELECT ( symbol: σ)

■ PROJECT ( symbol: Π)

Relational Algebra Operations from Set Theory:

■ UNION (∪)

■INTERSECTION (∩)

■DIFFERENCE (−)

■CARTESIAN PRODUCT (X)

SELECT (Symbol: σ)

(i) General form σ_c(R) with a relation R and a condition C on the attributes of R.

(ii) The SELECT operation is used for selecting a subset with tuples according to a given condition.

(iii) Select filters out all tuples that do not satisfy C.

STUDENT:

Table A

 σ_course = “Big Data” (STUDENT ):

PROJECT (symbol: Π) :

(i) The projection eliminates all attributes of the input relation but those mentioned in the projection list.

(ii) The projection method defines a relation that contains a vertical subset of Relation.

(iii) Example 1 using Table A

Π_course (STUDENT)

Result:

Course

Big Data

R language

Python Programming

Course

Big Data

R language

Python Programming

(iv) Example 2 (using Table A)

Π_course (STUDENT)

Result:

UNION (Symbol: ∪) :

(i) It includes all tuples that are in tables A or in B. It also eliminates duplicates. Set A Union Set B would be expressed as A ∪ B

(ii) Example 3

Consider the following tables

Result:

SET DIFFERENCE ( Symbol: -):

(i) The result of A - B, is a relation which includes all tuples that are in A but not in B.

(ii) The attribute name of A has to match with the attribute name in B.

(iii) Example 4 ( using Table B):

Result:

Table A - B

cs4 Padmaja

INTERSECTION (symbol: ∩) A ∩ B :

(i) Defines a relation consisting of a set of all tuple that are in both in A and B. However, A and B must be union-compatible.

(ii) Example 5 (using Table B)

PRODUCT OR CARTESIAN PRODUCT (Symbol: X)

(i) Cross product is a way of combining two relations. The resulting relation contains, both relations being combined.

(ii) A × B means A times B, where the relation A and B have different attributes.

(iii) This type of operation is helpful to merge columns from two relations.

Cartesian product : Table A x Table B

5.  Explain the characteristics of DBMS.

Ans.

Characteristics of Database Management System

Data stored into Tables : Data is never directly stored into the database. Data is stored into tables, created inside the database. DBMS also allows to have relationship between tables which makes the data more meaningful and connected.

Reduced Redundancy : In the modern world hard drives are very cheap, but earlier when hard drives were too expensive, unnecessary repetition of data in database was a big problem But DBMS follows Normalisation which divides the data in such a way that repetition is minimum.

Data Consistency : On live data, it is being continuously updated and added, maintaining the consistency of data can become a challenge. But DBMS handles it by itself.

Support Multiple user and Concurrent Access : DBMS allows multiple users to work on it(update, insert, delete data) at the same time and still manages to maintain the data consistency.

Query Language : DBMS provides users with a simple query language, using which data can be easily fetched, inserted, deleted and updated in a database.

Security : The DBMS also takes care of the security of data, protecting the data from unauthorized access. In a typical DBMS, we can create user accounts with different access permissions, using which we can easily secure our data by restricting user access.

DBMS Supports Transactions : It allows us to better handle and manage data integrity in real world applications where multi-threading is extensively used.