Database MCQ - ER-model & Relational Model

56:  

Consider a relational table with a single record for each registered student with the following attributes.
1. Registration Num: Unique registration of each registered student.
2. UID Unique identity number, unique at the national level for each citizen.
3. Name: Name of the student.
4. BanIcAccount Num: Unique account number at the bank. A student can have multiple account or joint accounts.                This attribute stores the primary account number.
5. Hostel_Room: Room number ofhe hostel.
                     Which ofthe following option is INCORRECT?

A.

BankAccount Num is a candidate key.

B.

Registration Num can be a primary key

C.

UID is candidate key if all students are from same country.

D.

If S is a superkey such that S ∩ UID is NULL then S  ∪ UID is also a superkey.

 
 

Option: A

Explanation :


57:  

The following functional dependencies hold for relation R(A, B, C) and S(B, D, E) B —> A, A —> C , the relation R contains 200 tuples and relation S contains 100 tuples. What is maximum number of tuples possibles in natural join R  and S ?

A.

100

B.

200

C.

300

D.

400

 
 

Option: A

Explanation :


58:  

 Which structure is the hierarchical model based

A.

Tree

B.

Graph

C.

Linked List

D.

None of the above

 
 

Option: A

Explanation :


59:  

In the relational model, the number of attributes and number of tuples iri a relation are termed as __________and ______________respectively

A.

Cardinality, domain

B.

Degree, cardinality

C.

Domain degree

D.

Cardinality, degree

 
 

Option: B

Explanation :


60:  

 In domain relational calculus we create a variable for every

A.

Row

B.

Column

C.

Table

D.

None of the above

 
 

Option: B

Explanation :



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