Concept of Dbms

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CONCEPT OF DBMS

Edumate Questions

1. Give an example of

RDBMS package

Ans: Oracle, SQL Server,MS

Access,Foxpro, Dbase etc2. Select the property which

is desirable for a database

(a) Redundancy (b)

Inconsistency


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Integrity (d) Complexity

Ans: Integrity

Redundancy means

duplication of same data in

different places of the

database.

Inconsistency:

Redundancy may cause

inconsistency.

3. Pick the odd man out


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(a) Create(b) Select (c)

Update (d) Insert

Ans: Create. It is a DDL

command. All others are

DML commands

4. Name the key that acts as a

candidate key but not a

primary key

Ans: Alternate key


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5. ..is the ability to

modify a scheme definition in

ijne level without affecting

the scheme definition in the

next higher level

Ans: Data Independence

6. For accessing data from a

database

provides an interface with

programming languages


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Ans: SQL or DML

7. Consider the table with the

following fields Name, Roll

Number and Mark for a set of

students. A field among

them, which is suitable for

primary key, Justify answer

Ans: Roll Number

Roll Number can be used to

identify a student uniquely.


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Roll No cannot be repeated

ie. No two students have

same Roll Number

8. For catering to the need of

users, a database is

implemented through three

general levels. Name the

three levels and discuss them

Ans: The three levels are

1. Physical Level


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Physical level describes

how the data stored in storage

medium. This is the

lowest level. At this level

records will be stored in an

actual storage location

2. Logical Level

This level describes what

data are stored in the

database. It describes the


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relationship exist among

data. Here records are

defined, the type of data is

determined, relationships

are specified

3. View Level

This is the highest level. It

is closest to users, this level

concerned with the way


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in which the users view the

data

9. You have to present a

seminar on the topic Keys in

RDBMS prepare a seminar

report

View Level

Logical Level

Physical Level


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Ans: Keys are used to

identify the tuples in a

relation. The important keys

are

1) Primary key: Primary key

is a set of one or more

attributes used to identify a

tuple uniquely in a

relation. Primary key can

not be repeated


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Eg: Reg No. in student

relation

2) Candidate key: Keys that

can act as a primary key is

called candidate key. They

are the candidate key. It is

used to identify a tuple

uniquely

Eg: SI. No., Adm. No. etc

in student relation


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3) Super key: A

combination of primary

key with any other

attribute or group of

attribute is called super key

Eg: Reg. No. + Name in

student relation

4) Foreign key: When a

primary key of one

relationis also available as


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an attribute in aother

relation, that attribute is

called foreign key of the

relation. Foreign key helps

to attain data integrity

5) Alternate key: A

candidate key that is not a

primary key is known as

alternate key


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10. There are different data

models of which one is

currently used in all business

transaction. Specify it and

discuss details

OR

Remesh doing relational

operation in which he used

different tables for

manipulation.


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Which data model he is

using? Discuss in detail

Ans: Relational Data Model

Relational data model uses

a collection of tables to

represent data and its

relationship.

Important features are:

Represent data in form of

rows and column


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Rows represents records

and column represents

attributes or fields

A row is known as tuple

and column is known as

attributes

A relation can be

represented using a named

tableIt is developed by J.F. Code


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Eg. N

ame

Reg

No.

Mark

Ra

him

R

oy

Jo

sy

138

0

138

1

132

48

55

58


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11. Consider the following

table and write the relational

algebra operations for the

following.

DEPOSIT

Acc

No

Name Branch Amoun

100

1

100

2

Kumar

Salim

Fida

John

Calicut

Trivandru

m

Kottayam

10,000

25,000

18,000

30,000


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100

3

100

4

100

5

Raju Kannur

Thrissur

5,000

(a) To display those tuples

fr


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om DEPOSIT relation

where amount is greater

than

25,000

(b) To display only Acc No.

and amount of all

depositors

Ans: (a) s amount> 25,000

(DEPOSIT)


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(b) Acc No, Amount

(DEPOSIT)

12.

STUDENT

GRADE

Reg

No

Name Scores

101

102

103

104

105

Preethi

Anupama

Ruksana

Nancy

Anu

70

68

94

87

77


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Consider the relations

STUDENT and Grade

given above and predictthe output of the following

Reg

No

Scores Grade

101

102

103

104

105

70

68

94

87

77

B+

B

A+

A

B+


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2.Reg No Scores

101

102

103

104

105

70

68

94

87

77


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3.

4.

Reg No Score Grade101

105

70

77

B+

B+

Reg No Name103

104

105

Ruksana

Nancy

Anu


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5.


Relations

Reg No Scores Grade101

102

70

68

B+

B


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R1 R2

Reg No Name Grade

1200

1201

1202

Babu

Lulu

Sunu

A

A+

B

Reg No Name Grad

1203

1201

Biju

Lulu

D

A+


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Show the output of the

following relational

operations

(a)R1-R2 (b) R1 R2

(c) R1 R2

Ans: (a) R1-R2

Reg No Name Grade1200

1202

Babu

Sunu

A

B


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(b) R1 R2

(c) R1 R2

Reg No Name Grade1200

1201

1202

1203

Babu

Lulu

Sunu

Biju

A

A+

B

D

Reg No Name Grade1201 Lulu A+


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Data which is composed

off more than one single

valued data is known as multi

valued attribute eg. Date

of birth


table and write relational

algebra operations for the

following


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DEPOSIT

Acc

No

Name Branch Amoun

100

1

100

2

Kumar

Salim

Fida

John

Calicut

Trivandru

m

Kottayam

10,000

25,000

18,000

30,000


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100

3

100

4

100

5

Raju Kannur

Thrissur

5,000

(a) To display those tables

from DEPOSIT relation

where amount is greater than

25,000


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(b) To display only Acc

No. and amount of all

deposits

Ans:

(a) s Amount> 25,000

(DEPOSIT)

(b) Acc No, Amount (DEPOSIT)


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