Functional-Dependency Theory - DBMS

1.

Inst_dept (ID, name, salary, dept name, building, budget) is decomposed into
instructor (ID, name, dept name, salary)
department (dept name, building, budget)
This comes under

   A.) Lossy-join decomposition
   B.) Lossy decomposition
   C.) Lossless-join decomposition
   D.) Both a and b

Answer: Option 'D'

Both a and b

2.

Suppose we wish to find the ID’s of the employees that are managed by people who are managed by the employee with ID 123. Here are two possible queries:
I.SELECT ee.empID
FROM Emps ee, Emps ff
WHERE ee.mgrID = ff.empID AND ff.mgrID = 123;
II.SELECT empID
FROM Emps
WHERE mgrID IN
(SELECT empID FROM Emps WHERE mgrID = 123);
Which, if any, of the two queries above will correctly (in SQL2) get the desired set of employee ID’s?

   A.) Both I and II
   B.) I only
   C.) II only
   D.) Neither I nor I

Answer: Option 'A'

Both I and II

3.

Consider a relation R(A,B,C,D,E) with the following functional dependencies:
ABC -> DE and
D -> AB
The number of superkeys of R is:

   A.) 2
   B.) 7
   C.) 10
   D.) 12

Answer: Option 'C'

10

4.

We can use the following three rules to find logically implied functional dependencies. This collection of rules is called

   A.) Axioms
   B.) Armstrong’s axioms
   C.) Armstrong
   D.) Closure

Answer: Option 'B'

Armstrong’s axioms

5.

Which of the following is not a Armstrong’s Axiom ?

   A.) Reflexivity rule
   B.) Transitivity rule
   C.) Pseudotransitivity rule
   D.) Augmentation rule

Answer: Option 'C'

Pseudotransitivity rule

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