Dbms(Engineering > Computer Science And Engineering ) Questions and Answers

Question 1.

Suppose x is  a component of some tuple and the domain for that component is integers. If X has the value NULL, what is the value of

I  0*X

II  x - x


  1.    NULL, NULL
  2.    0, 0
  3.    NULL, 0
  4.    0, NULL
Explanation:-
Answer: Option A. -> NULL, NULL

When we operate on a NULL and any value including another, NULL, using any attribute operator the  result is NULL.



Question 2.
The primary key is selected from the:



  1.    composite keys.
  2.    determinants.
  3.    candidate keys.
  4.    foreign keys.
Explanation:-
Answer: Option C. -> candidate keys.


Question 3.

A network schema


  1.    stores data in tables
  2.    permits many-to-many relationship
  3.    Restricts the structure to one-to-one relationship
  4.    None of the above
Explanation:-
Answer: Option B. -> permits many-to-many relationship


Question 4.
A relation is in this form if it is in BCNF and has no multivalued dependencies:



  1.    second normal form.
  2.    third normal form.
  3.    fourth normal form.
  4.    domain/key normal form.
Explanation:-
Answer: Option C. -> fourth normal form.


Question 5.
A relation NADDR is defined with attributes Name (unique), Street,City,
State and Zip. For any given Zip, there is just one City and state. What
is the highest normal form satisfied by above decomposition?



  1.    1NF
  2.    2NF
  3.    3NF
  4.    BCNF
Explanation:-
Answer: Option B. -> 2NF


Question 6.
When the values in one or more attributes being used as a foreign key
must exist in another set of one or more attributes in another table, we
have created a(n):



  1.    transitive dependency.
  2.    insertion anomaly.
  3.    referential integrity constraint.
  4.    normal form.
Explanation:-
Answer: Option C. -> referential integrity constraint.


Question 7.

In context with Relational algebra, which of the following are unary operations

I   SELECT

II PROJECT

III UNION

IV PRODUCT


  1.    All are binary operations
  2.    I and II Only
  3.    II Only
  4.    I and III Only
Explanation:-
Answer: Option B. -> I and II Only

SELECT and PROJECT are called unary operations because they operate on one relation.



Question 8.
A race condition occurs when
  1.    two users of the DBMS are interacting with different files at the same time
  2.    two concurrent activities interact to cause a processing error
  3.    both (a) and (b)
  4.    None of these
Explanation:-
Answer: Option B. -> two concurrent activities interact to cause a processing error


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