Classical

Database MCQ - ER-model & Relational Model

46:  

An instance of relational schema R (A, B, C) has distinct values of A including NULL values. Which one of the following is true?

A.

A is a candidate key

B.

A is not a candidate key

C.

A is a primary Key

D.

Both (A) and (C)

 
 

Option: B

Explanation :


47:  

Consider the join of a relation R with relation S. If R has m tuples and S has n tuples, then the maximum size of join is:

A.

mn

B.

m+n

C.

(m+n)/2

D.

2(m+n)

 
 

Option: A

Explanation :


48:  

The natural join is equal to :

A.

Cartesian Product

B.

Combination of Union and Cartesian product

C.

Combination of selection and Cartesian product

D.

Combination of projection and Cartesian product

 
 

Option: C

Explanation :


49:  

 Which one of the following is not true for a view:

A.

View is derived from other tables.

B.

View is a virtual table.

C.

A view definition is permanently stored as part of the database.

D.

View never contains derived columns.

 
 

Option: C

Explanation :


50:  

 A primary key if combined with a foreign key creates

A.

Parent-Child relationship between the tables that connect them.

B.

Many to many relationship between the tables that connect them.

C.

Network model between the tables that connect them.

D.

None of the above.

 
 

Option: A

Explanation :




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